A stored procedure in SQL is a group of SQL statements that are stored together in a database. It is a prepared SQL code that can be reused over and over again, which allows you to pass the same statements multiple times, thereby enabling reusability. Stored procedures are created to perform one or more DML (Data Manipulation Language) operations on a database. They can be used to perform a wide range of database operations such as inserting, updating, or deleting data, generating reports, and performing complex calculations.

Stored procedures provide several benefits, including:

• Reusability: Multiple users and applications can easily use and reuse stored procedures by merely calling them.
• Easy to modify: You can quickly change the statements in a stored procedure as and when you want to, with the help of the ALTER TABLE command.
• Security: Stored procedures allow you to enhance the security of an application or a database by restricting the users from direct access to the table.
• Low network traffic: The server only passes the procedure name instead of the whole query, reducing network traffic.
• Increased performance: Upon the first use, a plan for the stored procedure is created and stored in the buffer pool for quick execution for the next time.

The basic syntax to create a stored procedure in SQL is as follows:

CREATE PROCEDURE procedure_name (parameter1 datatype, parameter2 datatype, ...)
AS
BEGIN
    -- SQL statements to be executed
END;

To execute a stored procedure, you can use the EXEC statement followed by the procedure name. You can also pass parameters to a stored procedure, so that the stored procedure can act based on the parameter value(s) that is passed.

Overall, stored procedures can save time and memory by consolidating and centralizing logic that was originally implemented in applications.