Dear Rastafari,
Post production is the the process the film goes through AFTER filming. It's when the music is put in place, the editing, the special effects, everything that wasn't or couldn't be done during filming. Often this takes a long time because of several reasons. The director might not be happy with the cut he made, the studio may not be happy with his cut, often directors will have to wait for the composer they've chose to become available, sometimes effects work can slow things down. I've heard some directors say on DVD commentaries that generally post production takes them 6-9 months. I guess when there's so much money at stake they don't want to rush things. Most films never have 2 month post production times but there are some of them. Spy Kids 3 because it was shot with a digital camera was put together overa three month period, that's what I heard, and our own fave, Exit Wounds was being edited while it was shot and got put out three months after shooting making it's post production a relatively fast 6 months.