Topology is the study of some properties of geometry or space that can remain unchanged after continuous shape change. It only considers the positional relationship between objects, without considering their shapes and sizes. Some important concepts in topology include connectivity, compactness, open set and closed set. These concepts are abstract and need to be deeply understood and mastered.

Topology is difficult, on the one hand, because its concept is very abstract, which requires high mathematical literacy and thinking ability to understand and master. On the other hand, theorems and proofs in topology are usually very complicated, which requires in-depth mathematical knowledge and skills to understand and apply.

Topology is also a very interesting and useful branch of mathematics. It is closely related to other fields of mathematics, such as algebra, geometry and analysis. The study of topology not only helps to promote the development of mathematics itself, but also helps to solve problems in other fields, such as physics and engineering.