Guild Wars 2 Dungeons are PvE instances for groups of up to 5 players. There are eight standard dungeons, plus a few that are only available during special events, and one special kind of dungeon called a fractal. The post only touches upon the eight standard dungeons.
Dungeons become available to players beginning at level 30 and additional ones unlock at later levels. Each dungeon has both a story mode and explorer mode. The following chart outlines which dungeons are available at what level.
Story mode is played through on the first visit to the dungeon and unfolds an aspect of the story of the Destiny's Edge group. They do not need to be completed in order but their plotlines will be more meaningful when the personal storyline has been completed up to the same level that the dungeon is unlocked.
Explorer mode is a more difficult instance which requires more co-ordination to play through and is unlocked after completing story mode. It deals with the aftermath of the events in story mode. The explorable dungeon story is told with fewer cutscenes and little exposition, and the player party is no longer joined by members of Destiny's Edge. The player is presented with at least three different paths to play through for each dungeon. The party votes on the option they will take through the dungeon and the majority determines on which path they take. The explorable mode dungeon is designed to be repeated, with player actions and decisions determining the occurrence of hidden or random events along with the choice of a path.
Items of Note:
1. Content does not scale depending on the number of players in the party so the difficulty remains constant.
2. Characters are dynamically leveled up or down to the level appropriate for the relevant story or explorable mode.
3. There are a lot of item drops. Have lots of inventory space and salvage kits!
4. If someone enters the dungeon instance while you are in the same world map zone, you will be given the option to teleport directly to their location without any cost.
5. While there are no strict gear requirements, please try and make sure you have equipment commensurate with your level and keep the upgrade slots filled in.
Dungeon Walkthroughs:http://gw2dungeons.net/
Guild Wars 2 Wiki:
http://wiki.guildwars2.com/wiki/Dungeon
Using Stealth to Skip Mobs: