A company database contains all the data that the company uses to conduct business.
The database consists of tables. Typically there would be an employee table, a customer table, a product table, etc.
A college registration system probably has tables for student, faculty, course, sections and rooms.
A customer table would have a row or record for each customer.
A customer table would have a field for each each piece of information such as name, account number, address, etc.
Fields are also called columns or attributes.
One (or more) field is unique and is called the key. The student id would be the key in a student table.
Database Terminology