Question about recharging AC

What is meant by "low side" or "low port" for recharging the AC system? What does it look like and where is it located?

I have a 6 cyl Alero.

Any information that will help me will be greatly appreciated. Please remember that I'm just a "shade tree mechanic" and I have no shade.

Also, how do I remove the AC compressor relay? If I try to remove it with my fingers, it will not come out. Can it be checked to see if it is still good and if so, how do I check it?

The low side port is where you replenish the R134a refrigerant. The port is located by the firewall below the alternator. The lines it is on feeds the evaporator core. There is a blue cap on it.

You can check the AC compressor relay by feeling or listening for a click and better yet with a multimeter. The relay is a micro-relay and plugs into a socket so it is removeable. You'll need to get a good grip to pull it out. Try rocking it side to side gently while pulling it out. Good luck!