What is the low side on 1991 Nissan Pickup (D21)

what is the low side

Asked by for the 1991 Nissan Pickup (D21)
The opposite of "the high side!"

The fitting to add more freon to the A/C system. I assume you have ask where to charge the A/C system and was told that. Instead of me typing a bunch of words, try youtube and search for a video on how to charge an A/C system. Bet you will find one!