Scam

How do you explain what a scam is to a 77 year old who is totally computer illiterate? She wanted to put one of her sewing machines on craigslist because she does not use this machine at all. So, I posted it for her and off we went. Well, today I got a response from someone who wanted to buy the machine, but didn't want to pick it up - they didn't need it just trying to help someone else out. They needed the full name of the person selling the machine, the address to send the check and then they would send a check for MORE than the amount if I would just wire some money to a friend and I could keep $50 extra dollars for my time in doing this for them. I told them that I wasn't interested in their illegal scheme - try someone else and I was done with them (except for reporting them to craigslist). Anyway, I told mom about it and she doesn't understand why I think this is a scam. Why would someone want me to wire money to someone else? Why don't they just wire it in the first place? How do they know that I would actually wire the money and not keep it? These are just a few of the questions I had to answer about this. Thank God that I was the one who got the e-mail and that I could step in and stop any activity before it happened. So easy to scam older Americans because most are just not computer savvy.