ok im getting ready to do a pulley and coupler change and i need to know what the tensioner is and how do i loosen it to let my belts loose when i do this

Follow the belt over the top of the SC pulley towards the firewall. The very next pulley (black, on an aluminum arm) is the tensioner. Get a ratchet (breaker bar works better) with the corrcect socket for the bolt holding the pulley to the tensioner, and use it to leverage the tensioner down. Hold it down and slip the belt off.

When putting it back, make sure the belt is resting correctly on all pulleys, especially the water pump.