This lecture is part of an online course on Category theory
This is the introductory lecture, where we give a few examples of categories and define them.
The lectures were originally part of a graduate algebra course, and give a quick overview of the basic category theory that is useful in algebra.
Recommended textbook: "Categories for the working mathematician", by S. Mac Lane.
For the other lectures in the course see https://www.youtube.com/playlist?list=PL8yHsr3EFj51F9XZ_Ka4bLnQoxTdMx0AL