This is going to be a pretty big word vomit, but hopefully it helps to give you a better idea of what the game is about.
There are five different world types.
Every player gets an Eternal Kingdom, which is their own personal world. This world comes with only a central default parcel (piece of land) that you can't build on. You can purchase, or craft in-game, parcels, buildings and defensive structures to place in your EK. You can invite other players to join your world, or they can invite you to theirs, and you can pool your parcels and buildings together to create a larger world. EKs can be used as a training ground for your guild, as you can control whether the EK is public or private, and whether PvP is on or off. You can also set up an EK to be a marketplace, though right now that isn't really working as intended. It's something they plan to address in the near future. The biggest issues working against it are the fact that players get logged off when AFK, and EKs shut down after a bit if no one is in them, so it's hard to keep an EK open. The other issue is that players can place vendors in the temples in other worlds, so no one bothers to visit EKs anymore. That is supposed to change as well.
As far as actually playing the game, you want to start out in a God's Reach world. God's Reach are PvE only worlds where you can level up and learn the basics of the game. They are in the process of building the new player experience (a basic quest system) to help players learn the game. Right now, the quest system only takes you to about level 8. There are two more parts coming that should hopefully take new players to 30. God's Reach worlds never end (they do for testing, but not once the game is live).
The Infected is the next world type. These worlds have PvP, but there is no inventory looting, and there are no winners and losers. It's just a constant 3-faction tug of war with a scoreboard that shows who is winning at any given time. The minimum level to join an Infected world is 15 (max level is 30 and you can reach max in 2-3 hours). Infected worlds never end (again, not for testing). This world type includes fighting over outposts, forts and keeps. The Infected world is usually only up when a Dregs campaign is not, due to low player population. For beta, we should see multiple of each world type.
Next are the Shadow, which are faction-based campaigns. The scoring is similar to the infected, though these worlds end and there is a definite winner. You also drop your inventory when you die, allowing other players to take it. This world type also includes fighting over outposts, forts and keeps. The minimum level for this world is 20. There are currently no Shadow worlds active, as the focus is on testing Dregs right now.
The last set of worlds are the Dregs. These are guild vs guild campaigns. In addition to fighting over outposts, forts and keeps, guilds can engage in city building. This allows them to upgrade keeps, adding different types of buildings and buffs. This is where the caravan system becomes more important, as you need the materials obtained from caravans to build up your city. The Dregs also includes the Divine Favor system, which is a set of cards with various goals for guilds to accomplish to earn points toward winning the campaign. There are a set of cards that are the same each season, though the points are awarded for what each guild accumulates within a specific season. Another set of cards is only available in a given season, and the following season, there will be a completely new set of cards. For example, there might be a card that rewards the top 3 guilds that sacrifice the most enemy heads to a certain god. The minimum level for the Dregs is 20.
Only the Shadow and the Dregs go through all four seasons, since they are the only worlds that end. God's Reach and Infected are both perpetual spring. The higher you go into each world tier, the better the potential rewards. For example, you won't find better than rank 4 and maybe a few rank 5 harvesting nodes in God's Reach. In the Dregs, you'll find ranks 8-10 (10 is the max). That risk vs reward structure extends to dropped items as well, like crafting recipes and tools, and disciplines.
It is recommended to join a guild and play with other players. The Shadow is faction-based, so you can join a pre-made team, and the Dregs also has default factions for players who aren't part of a guild, but your overall experience will likely be better in a guild. The game is pretty deep and there are many inter-dependencies, particularly in crafting. To a certain degree you can do everything yourself, but it would require multiple accounts and lot more effort on your part. It's just easier and a lot more efficient to work with other players.
An alliance system for the Dregs is in the works, which will enable guilds to ally with each other, and they are still working on the in-game guild tools. Right now all we have is guild chat. Guild creation and membership is handled entirely through the website right now, and it costs real money to make a guild (you are actually paying for the guild name reservation). Once the game is live, creating a guild will be free. You can search for guilds here: https://crowfall.com/en-US/guild or here: https://community.crowfall.com/forum/5-guild-recruiting/
Beyond the quests for the NPE, there isn't any hand-holding. The game won't tell you what you should be doing. It's entirely up to you and your goals. This is another good reason to find a guild, as they can help you figure that out.
Shadow and Dregs campaigns have import and export limits. When you join a campaign, you can only take so much stuff in with you, and at the end, you can only take so much out. How much you can take out will be dependent on how you do in the campaign (win, lose, kneel, quit). That logic isn't in yet, though. Right now, everyone can export the same amount regardless of the results. Different campaigns can have different limits.
Your characters can move between all worlds, though once they join a Shadow or Dregs campaign, they are locked to that campaign. You can unlock the character from the lobby, currently without penalty, but that may change in the future. Your inventory will move with you when moving between EKs, God's Reach and Infected World. For the Shadow and Dregs, you are always subject to the import and export limits. You have a central vault that is used by all characters on your account. There are currently some issues that they are working on in regards to giving us more storage space, as well as guild-based storage.
The game is set up to allow for a lot of experimentation. You can level a common vessel (the default body you get when you first create a character) pretty quickly. You can purchase most common quality disciplines from a vendor and try them out. When you get to the point where you get a better vessel (vessels are crafted by necromancers), you will need better quality disciplines, which are harder to obtain. You have to venture out into the Shadow and Dregs worlds to get those.
Understand that there are still things being worked on, there are still lots of bugs, and there isn't much balance. They know they need to do another pass on the disciplines and on class talents. And they are also still working on performance. It has gotten a lot better, but it still has a ways to go.
Now that you know all of that, you should also know that Beta will begin in the near future (1 to 3 months, most likely). At that time, anyone who created a Crowfall account will be invited, a few thousand at a time, based on when you joined. So if you want, you can wait until then and try it for free to see if you like it.
I hope that all helps. If you have any specific questions, just ask.