Set theory and category theory are both abstract theories that provide a framework for explaining various phenomena. Set theory, in particular, is composed of abstract concepts like sets, which can represent a wide range of things. Sets can be used as building blocks for concrete theories and can help unify and compare different theories. Functions, on the other hand, are relationships between sets that match each element of one set with exactly one element from another set. Different types of functions can express different types of relationships. Additionally, sets and functions are widely used in programming, where types serve a similar role as sets. Type theory is a more restrictive version of set theory that was developed to avoid paradoxes like Russell’s paradox.
https://abuseofnotation.github.io/category-theory-illustrated/01_set/