Can someone tell me about tramadol?

I had my gallbladder removed and im backk to wrk(cna).ive been hurting a lil and I cnt take my other pain pills while at wrk cause it make me sleepy....and im stilll feeling pain after 4wks of my surgery, so he gave me tramadol for pain......can someone tell,me more about it, that has taking it or heard about it? Does it make yu sleepy? And what are some side affects?......