Lafeu is a feisty old nobleman in the king of France's court. He's pretty chummy with both the king and the countess of Roussillon. He's a loyal guy and is very generous with Helen, going so far as to help set up a meeting between her and the king (2.1). Like the countess, Lafeu is one of Helen's biggest fans. He tells us over and over again that she's worthy of Bertram's love, despite her low social rank and lack of wealth.
In the play, Lafeu acts as a kind of spokesperson for the older generation's ideals and values and he's always bagging on the younger generation of men for being immature and shallow. For example, when a group of young noblemen snicker at Helen, Lafeu grumbles that they deserve castration for their bad behavior: "An they were sons / of mine I'd have them whipped, or I would send / them to th' Turk to make eunuchs of" (2.3.94-96). Yikes!
Lafeu values honor, virtue, and honestly above all else, which is why he absolutely hates Paroles, the play's resident liar/coward/shallow young man. In fact, Lafeu is one of the first characters to call out Paroles for being a phony. He even threatens to beat him up, despite the fact that Paroles is a lot younger.
mine honor, if I were but two hours younger, I'd
beat thee. Methink'st, thou art a general offense,
and every man should beat thee. I think thou wast
created for men to breathe themselves upon thee. (2.3.266-270)
Oh, snap! Lafeu is basically saying that Paroles was born to be his punching bag. The two men never come to blows but, if they had gone toe-to-toe, we imagine it would look something like the fight between Bob Barker and Happy Gilmore.