What are stored procedures and what are their advantages and disadvantages?

Stored procedures are precompiled SQL code stored in the database. Advantages: reduced network traffic (send procedure call not full SQL), security (grant access to procedure not tables), performance (precompiled, cached execution plans), encapsulation (centralized business logic). Disadvantages: vendor lock-in, harder to version control, debugging challenges, may not scale horizontally, logic split between app and database. Modern trend favors application-level logic.