Followers NPC are characters that can become your ally and are found all throughout Skyrim. Followers can be permanent or temporary due to Quests, fighting by your side, travelling along with you, carrying your items and performing tasks for you. You can only have 1 humanoid NPC and non-humanoid creature follower at a time but some quests with temporary followers can allow you to have multiple followers.
Followers will match the player level, keeping up until they reach their individual level limit. The level limit varies per follower with some followers reaching a limit at level 20 while some have no level limit such as J'zargo. Followers also gain different stats and skills per level, growing in their own combat roles as they level.
Who is the Best Follower?
Players may look for followers that they find interesting in the world and take them along, dialogue lines and voices are quite important factors to some when picking a follower to have as company on your journey, others might consider combat ability the most important factor from their followers instead. While it becomes difficult to suggest any single follower as a best fit to every player's ideal for what they want in a follower, there are a few that do stand out as good followers to consider.
One group of NPCs that are almost always great followers are the ones that count as essential NPCs and are therefore un-killable. They act as great distractions in combat and give the player the assurance that they will never have to worry about their follower dying, followers such as Mjoll the Lioness, Serana and Cicero just to name a few fill this role well. Another type of follower are the ones without level limit, keeping up with the player well into the late levels of the game such as J'zargo or Celann. An interesting follower that does both is Frea who is an essential NPC as well as having no level limit.
Players may also want to consider the mercenary options as powerful allies that are easy to obtain for a little coin, without needing to finish long complicated questlines.
Followers will try to equip the best equipment in their inventory, which often means the highest value Armor and Weapons. Followers also have a preference to Weapons and Armor that match their skills, they will prefer to wear the armor types that suit them. If your follower is equipping equipment that you don't want them to, remove it from their inventory.
Followers will not use up enchantment charges so equipping them with enchanted weapons is a good idea. See the Enchanting page for a list of enchantments that you can put on your weapons. Followers also shoot arrows without consuming them so give them the highest damage arrow you have to increase their effectiveness.
On death, you can recover the equipment by looting their corpse or by visiting their coffin in the Hall of the Dead near their home town.
Commands and Morality
Followers can be commanded out of combat to perform a variety of tasks, attacking enemies, picking up items, picking locks, looting etc. Lockpicks are not needed by followers to open locked doors or containers.
Most NPC's will either be moral or immoral which affects how willing they are to commit a crime on your order. Immoral NPCs will be willing to commit any crime you ask them to while moral NPCS will refuse to commit crimes. Moral NPCs will not report crimes you commit, if you do not commit the crime on them.