With your Garrison, you can have a wide variety of followers, such as those with professions, and you can send them off into the world to gather resources.  The more advanced your Garrison is, the longer the missions will be, but with better rewards.  Blizzard has said that managing your followers will be an important part of your garrison.

Your followers will all have a specific spec – tank, healer or DPS.

You can name all of your followers, as you can see in the screenshot below – Oprah Windfury got a chuckle from the audience at Blizzcon.

Your followers each have a set of abilities to assist them on missions.

Followers also come in common (white), uncommon (green), rare (blue) and epic (purple), similar to how pets come in different rarities.  It is not known if you can upgrade rarities, or simply their level.

All followers seem to start at level 90, and they need to earn XP to level up for each level.   Once your followers reach max level (believed to be 100, but could be level 95 based on screenshots), you then work on raising their ilevel after that.

Each follower has its own detailed description as well, so you can pick and choose the mission he or she is best suited for.

About followers:

• Many ways to collect
• Level up by running missions
• Increase ilevel once maxed out
• Followers have abilities and traits
• Quality / Rarity (like pets)
• Customize with names

The ways to collect followers not only include finding them in your Inn, but also by faction, gold, quests, dungeons, etc.  They are also investigating an option where we could transmog our followers.