Persistence in the world of computer software indicates that some data has some longevity - that it persists.
To enable persistence the data must be remembered in some retrievable way. This may range from storing in a named variable to enable persistent access within even a program fragment, to writing the data to non-volatile media such as a hard disk drive.
Conventionally, it is this last category that is meant by persistence.
Absolutely. Without persistence at various levels computer systems would not make sense or do anything useful.
A java-based persistence mechanism is central to the Cut The Crap Software.
The core package is GPO - Generic Persistent Object - and this
provides more than simple persistence, but a powerful generic object model with
scalable persistence designed in from the beginning.
Please check out the main website for more information and free downloads.