Followers complete missions for various purposes including to level up their own experience. Successful missions yield resources needed to develop your Garrison and give you the opportunity to acquire loot for your own character(s). Based on these objectives the missions are designed to make your followers progress from level to level.
A full rundown of all available missions, complete with videos and guides for each, will be posted when Garrisons are activated in World of Warcraft.
Fun fact: Followers are great for solo play but the system also has multiplayer elements available. When you send a party of followers on a mission you can have them join forces with your guildmate’s followers, even if your guildmate is offline.
Followers grow in power in a way that mirrors player’s progression. From levels 90–100, followers will gain character levels, which have a significant impact on their abilities and mission success chance. They’ll also increase their item level as you equip them with follower-specific gear; once they’ve reached level 100, equipment will have a larger role to play in their overall effectiveness. battle.net
Followers will wear their own special brand of armor, not the pieces you can equip, so you won’t have to decide if you should keep a piece or armor of give it to your followers.
Used to level up followers, though high level quests have a chance to earn loot for your character
Takes longer than quests, but has a higher chance for loot
Guaranteed to earn player loot, but take longer and are harder. Dungeons require five followers
Raids take days to complete. They unlock when at least ten followers get to level 100. Transmog missions for lower raids will sometimes become available.