“Dead” means having 0 current life. It is not a separate state, just a shorthand name for checking whether life is currently 0.
There are no gameplay or quest differences (increased drop rates, stronger monsters, etc). The only difference is that Hardcore has permanent death as an extra challenge, by means of moving you to Standard. (The admins will not move your character back if you die, except in extreme cases like game patches adding dangerous and widespread bugs.)
The character is sent to the Hardcore league. If you want to move to Standard, enter an area and die. Certain races with increased drop rates, such as Descent, send your character to an unplayable null league instead until you delete them.
There are currently 10 acts of increasing difficulty in the game. Acts are split into two parts, with Part II revisiting Wraeclast in a changed environment.
When you create a new character, you specify what league you want them to join, which is essentially the game type.
Currently, there are four permanent leagues: Standard, Hardcore, and the Solo Self Found (SSF) variants.
A new ‘challenge’ league is created every 3 months or so, which is split into 4 leagues:
These challenge leagues always have a unique mechanic on top of the standard or hardcore death rules. When these challenge leagues end (usually after three months), the characters in these challenge leagues return to their respective ‘base’ league type (standard, hardcore or the SSF variants) – along with all their inventory and stash items.
Characters in the hardcore challenge league are moved to the basic standard league when they die (just like in normal hardcore). Characters in the standard challenge league remain in that challenge league after they die (they are not moved to the regular standard league until the current standard challenge league ends).
Solo Self Found characters can be transferred to their base league with a click of a button.
Characters can be moved between leagues (usually towards the Standard league) when certain events happen. Usually, at the end of a ladder race/reset, characters are moved back to Standard so they can keep being played after the event. There are prizes for events, usually cosmetic microtransactions items.