Questions about LSD?

I've never done acid, but I'm very interested to try it. Before I pursue it, however, I'd like to know more about it and I can't seem to find the information elsewhere online, so I thought I'd try to get it from people who actually know what they're talking about. When high on LSD, how obvious is it to other people? I smoke weed so please use that as a comparison. Obviously on acid there are hallucinations, but how far from the real world are you? Say you were walking down a street, would you actually see a street at all? Or something completely different? I'm interested in the actual visual effects of it, really, and what a high person looks like to everyone else. Much appreciated, and sorry if I come across as dumb, but I've never done LSD so know very little about it.

TL;DR: please tell me what you see when you're on acid, compared with what is actually there.