Kent is Lear's servant. He's also the guy Lear banishes in the first act after Kent warns his king not to disown Cordelia. The thing to know about Kent is that he is loyalty personified. He would do anything for Lear, even though the King treats him badly and kicks him out of the kingdom.
After Lear boots Kent to the curb, Kent runs off and disguises himself as "Caius," just so he can get a job serving Lear again. Kent/Caius then proceeds to follow Lear all over the countryside, which is pretty uncomfortable, given that Lear and his entourage are homeless and the weather's pretty lousy out on the heath.
At the play's end, Kent is offered the job of co-ruling the kingdom (since Lear's entire family is dead). What does the ridiculously loyal Kent do? He says, "No thanks" and implies that he's going to commit suicide so he can be with his "master" (Lear). Yikes! What's Shakespeare trying to say? That Kent's loyalty as a servant is admirable? Or that Kent's devotion to Lear is just plain stupid?
Kent, as we've already hinted, is also notable for speaking honestly, which is a pretty rare in King Lear. Kent's not afraid to be blunt when he tells Lear he's a fool for believing that Goneril and Regan care about him or, when he tells Cornwall that he doesn't like the looks of his face. (This is a pretty risky thing to do, especially given Cornwall's penchant for plucking out the eyes of his enemies.) In Shakespeare's play, it turns out that having a big mouth is a good thing—we might even say it's a noble quality. We talk about this in our theme discussion of "Language and Communication," so check it out if you want to know more.