Yeah, you walk around you have all this equiptment. You can pull it out whenever. There are many ways to get through, well let's say a warehouse. There are 7 guys in it. You can pull out the good ole assault rifle and start shooting, you'll be revealed by them and they'll call for reinforcements. Not good. Or you can sneak around. Throw empty gun clips to make a noise. Knock on a crate then run around. Throw a porno magazine on the ground to distract them. Hideo Kojima (creator of game) made it that your gun is your last option as a spy. But if you need to use your tranqulizer gun, it knocks them out for a while. Then you have your vital items which help you out. There is a cardboard box so whenever you're spotted, whip it out to confuse them. Doesn't always work but it's a last resort.
I can't explain it well though. Oh, and if you have no weapons there is always CQC which is close quarders combat. I don't remember in MGS 1 if you could grab peoples neck, I think it was MGS 2 or 3.
The gameplay is very good in short. But the thing that beats the game is the story. I don't know if you'll like MGS 2's story, but MGS 1 and MGS 3 have a movie like quality script.
So go out and get MGS 1 already!