What's a check?

I went by Home Depot this evening to pick up some trim for my house.  I gathered up my stuff and got in line.  There was only one person ahead of me, but it was taking forever.  I got a little closer and noticed it was old man (hey, I am one!) who was writing out a check.  I was intrigued.  It has been about six months since I saw someone writing a check in public.  The man finally left, and it was my turn.  I mumbled to the cashier, “Wow, that was freaky!  Writing a check!”  She smiled and answered, “I’ve never even written a check!”  Are we living in a new world or what?!