Theme functions

Ok, so I see WordPress has many functions to get the output to show. I would like a little help in this matter. I’m making a plugin that will show an icon with each post. I was wondering how I could output the post id? I was looking through the code and can’t see it anywhere.

Thanks in advance,
Lang

PS. I’d love it if someone could talk to me regarding this. lang14 [at] gmail [dot] com