A procedure is a set of SQL statements that can be stored in a database. It can accept input parameters, perform some action (such as a query or update) and return a result. It is typically used for tasks that are performed frequently or that need to be encapsulated for reusability.

A function is similar to a procedure, but it returns a value to the calling program. In a function, the return type must be specified and the function must return a value of that type. Functions can also be used to perform calculations or transformations on data.

Both procedures and functions can be used to modularize code, improve performance and increase the maintainability of a database. However, they differ in their capabilities and use cases. Procedures are generally used to perform actions, while functions are used to return values. Functions can be used in select statements and other expressions, while procedures cannot.