This series of posts explores the concept of table functions in PostgreSQL and their implementation in YugabyteDB, a distributed SQL database. Table functions are a type of function that returns a computed row set that depends on actual arguments invoked. They can be used in the from list of a subquery or in arbitrary combination with tables and views. Built-in SQL table functions include generate_series(), unnest(), and values(). User-defined table functions can also be implemented using return next or return query statements, allowing for more flexibility and customization. Understanding table functions is crucial for implementing business logic inside a database and can help optimize application design. The series covers the basics of table functions, their implementation in YugabyteDB, and provides examples to demonstrate their use cases.