IM what???

I received a request for my IM address from a friend of mine, and I have no clue how to do this. I have become lazy in learning new computer things. I know IM is not new. At my previous job, I watched several of the ladies signed on and IM each other and their friends. I just never did. I feel like I have been left behind. Now, I work for a different company who watches internet usage like hawks. I would like to start IMing with some of my friends, but I am terrified of of the Company's System guys. Oh well, I guess I will stay in the dark ages.