The Pubs database provides a set of fictional pieces of information about publishers, authors, titles and sales of books.
It is now considered obsolete; it is no longer provided with SQL Server since the 2008 version.
The tables and fields should be quite obvious. They have names such as Authors, Titles, etc., which reflect their content. And the fields also have obvious names explaining what they contain.
If you want to explore the relationships between tables (foreign keys) you can use the option to create a database diagram in SQL Server Management Studio (SSMS). Simply add all of the tables in the database to a new diagram and let SSMS arrange them automatically. The Pubs database is small enough that a single diagram can contain all the tables without becoming confusing.