Why when I press the clutch does my engine rev without me stepping on the gas?

What is your question?

when I press down the clutch to change gears the rpms go up really high then back down, but if I ride the clutch it goes back up then down again with me never touching the gas. Sometimes when I am idling it will continue to go up down (rpms as if I am reving the engine and letting it go), but not as much as when I initially press the clutch down? Is my clutch going out or is it just an idling issue?