Preventing Sleep is a display and system sleep prevention APP.
When the power saving (idle) needs to be started,Preventing Sleep can temporarily cancel the power saving settings (like:system or display) until you turn off.
Q:Why my Mac doesnt sleep when Preventing Sleep function is turned off
A:Preventing Sleep turning off function is work actually, but some app may still use Prevent Display or System function. You can click "Prevent Process Lists" to get more detail.