will memory-swap data on my HD be deleted after using?

let's say my RAM has run out and is now relying on the HD storage to replace it (memory swapping)

I noticed a decline in my HD storage, then after about 2 hours, I closed the program.

Will the memory swap files stored in the HD be deleted after I close the application or when it is no longer needed? is it temporary?

If so, when will it be deleted? a few hours after i close the program? or is it deleted immediately when the RAM is available again?

Detailed answers are greatly appreciated.