Build codes in glove box

Where can I find the meaning of the build codes on the label in the glove box in my 2001 Silverado? I suppose the factory manuals would have these, but there must be some place on the web that would explain these 3 digit codes.

can do a google search for GM RPO and I think there is a list a gm-trucks.com

RPO RPO. I know about these but all I could think of was build codes. Got the info I needed, thanks to you, Jeremy!

Try this link. Select year and enjoy!

http://gm-trucks.com/RPO_index.shtml