I am/was a Beta tester for Disney POTC.
(That gives me free access and unlimited usage now)
The game officially went online last month.
There is a basic "free" membership that gives you limited access to things like:
number of weapons you can own or carry, level of ships you can achieve, etc.
I don't have all the details on the membership options.
More involved access, costs varying amounts.
The game involves a "Quest" to hunt down and re-form Jack Sparrow's crew for a mission to capture the Black Pearl. The game is designed to be a single player adventure, but you constantly interact and "team up" with other online players throughout the game. Its a long and involved quest consisting of many different smaller quests and missions. You can always and at any time, go off on other quest, missions, solo adventures, or team up with other players for all kinds of things.
Sailing different ships and battling the Navy or the East India Trading Co. ships is one of the most interesting aspects of the game. There is a large ocean containing many different Islands and Ports for you to travel to and "play" in.
The "quest" has some very tedious and monotonous parts...and yet it is unbelievably addictive.
You can even go into one of the Taverns on the many different islands and sit down to play Poker or Blackjack!
And of course there are so many other "live" players...many new people to interact with and meet. I have also joined the POTC online Forum group to be more involved.