Group theory involves highly abstract concepts and proofs. In group theory, the object of study is groups, that is, algebraic structures composed of sets and binary operations on sets. This abstraction makes it difficult for beginners to intuitively understand the meaning and application behind it.

Proof in group theory involves complex logical reasoning and algebraic skills, and requires a solid mathematical foundation and good abstract thinking ability. It takes a lot of time and energy to learn and master group theory, which also increases its difficulty.