Persistence is the term used in computer science to describe a capability used by a computer programmer to store data structures in non-volatile storage such as a file system or a relational database.
Without this capability data structures only exist in-memory, and will be lost when a program exits. Persistence allows, for example, a program to be restarted and re-loaded with the data structures from a previous invocation of the program.
Examples of persistence are using Java serialization to store Java objects on disk or using J2EE to store Java enterprise beans in a relational database.