1996 Chevy Lumina Strange air conditioning problems

Greetings,
Before I start, I'm going to make it clear that I know absolutely nothing about automobile repair. I'm asking around about this problem, in hopes of eventually being able to fix it myself, rather than just dropping it off at a shop and paying someone to fix it (even though I suppose it's possible that that might be the only solution). Okay, anyway! My car is having air conditioning problems. When the A/C is turned on it, expectedly, takes a little bit to get cold and never gets super cold. But here's the weird thing - it sounds like it's working, but produces hardly any air at all. When I give the car gas in park, there is no difference in air output; however, when the car is put 'under power' when accelerating, there is a noticeable sound difference in the A/C system and the air blows out of the defroster. When the car isn't 'working' to get somewhere, even if the gas is being applied, it defaults back to the air vents with insignificant output. I believe the sound difference is just the sound of the air being routed through the defroster. I don't know what the problem is, but I know that on summer days like today, it sure is frustrating to have to sit in the scorching heat of that closed up car! Windows help, but my hair is long and it ends up blowing in my face and impairing my driving (not good.) I'm just curious to know why the air conditioner is responding to the engine like this and wonder if the problem is easily resolved. Perhaps I should read a bit about how A/C systems work in automobiles.

Thanks for anything you have to say about the matter.