2001 Toyota Celica Car stalling and not meeting performance

My 2001 Celica is having trouble when it starts up. It starts, revs, and then just stalls. I have to give it gas just so that it can stay on, and once it goes back to neutral when I come to a light, it stalls again. The check engine light came on and I bought a scanner. The scanner only reads P0171. Which is "System Too Lean (Bank 1)". I'm not sure what this means, but the biggest thing is that I'd like to know what Bank 1 means.