The article below provides a brief summary on the topic. For something more exhaustive, I recommend getting this manual. I can't recommend it enough, both as a game walkthrough and a leveling guide – it personally helped me to get from level 25 to 50 in 4 days.
Instance dungeons will also exist in the elder scrolls online; these are areas where you can only see the group that you entered with. These instance dungeons will deliver a more contained story-driven experience for a group of players. What are instance dungeons? Basically, think of any dungeon from World of Warcraft. The only people that are going to be inside that dungeon are the people that you joined with.
In-game PvE in ESO, it will feature heroic modes of each of these instanced dungeons, which are more than just a difficult version of the same content. The heroic dungeons extend the story of the normal mode version by adding a climatic and challenging in-game experience. In addition, the game has the large raids that pit multiple groups of players against powerful and iconic bosses. In addition, ZeniMax is also working to develop a “mega dungeon.” They like using that ‘mega’ word in this game’s development, don’t they? This dungeon is going to be reminiscent of Darkness Falls in Dark Age of Camelot. Basically, it’s a dungeon where depending on the current reigning faction in the world, in the PvP world, that will determine who will be able to enter this dungeon.
There is not a lot of information known to the public right now. We don’t know a lot of specifics about these dungeons, we just know how they’re going to work and that there’s going to be a lot of them.
The article above provides a brief summary on the topic. For something more exhaustive, I recommend getting the ESO strategy guide. I can't recommend it enough, both as a game walkthrough and a leveling guide – it personally helped me to get from level 25 to 50 in 4 days.