Bertie Wooster is a upper-class gentleman; he has his Club, he has his friends (all of whom have strange nicknames), he has his female friends with whom he tries to avoid romantic entanglements, and most of all, he has his Aunts, who are to be feared. Bertie often gets into tight situations either with his friends, or trying to avoid the females, or avoid the Aunts. Unfortunately, while Bertie is blessed with an upper-class life style, he was set off in life with an average sized helping of brain power... or maybe even less-than-average sized.
This is where Jeeves comes into things; Jeeves is a gentleman's gentleman, the ultimate man-servant. He knows which shoes go with which suit; what to wear to to every event; and what to say in every situation. And while Bertie might be lacking in the brains department, Jeeves is overflowing with them. His keen mental powers are called upon time and again by Bertie to help him out of the current scrape, which Jeeves does with understated aplomb.