In Neo4j, user-defined procedures are used to provide better performance, scalability, productivity, ease of use and security. These procedures can be created using the @Procedure annotation, which takes any Cypher type as parameters and returns a stream of Data Transfer Objects (DTO). When procedures write to the database, the @PerformWrites annotation should also be used. User-defined procedures are best suited for common tasks or frequently used tasks, and not for every single purpose.