Access is a complex database application. It is useful for handling multiple tables of data. For instance in a business you have sellers, stock items, buyers, transactions. Or in a school you have teachers, pupils, courses, coursework, exams, grades, etc. all of which relate to each other in different ways.
Access can build multiple relations ("one-to-many" relations) between different tables. You can design sophisticated user entry forms, reports, update queries etc. I suggest you get hold of a book like "Access for dummies" which walks you through the basics.