Humphrey Appleby is a character in a TV show called "Yes Minister" and "Yes Prime Minister". He is a very clever and sneaky government official who always tries to be in control of things.
To put this in simpler terms, imagine you are playing with your friends and one of them always wants to be the boss and tell everyone what to do. That's kind of like Humphrey Appleby. He always wants to be in charge and make all the important decisions.
He works for the government, which means he helps by making decisions that affect the whole country. But sometimes, he tries to do things his own way or make decisions that only benefit himself or his friends. That's not very fair, is it?
Overall, Humphrey Appleby is a very smart but sometimes not very nice character in a TV show about politics.