What is the ADF in printers and scanners?

I had some trouble just trying to add my lexmark s410 printer to my computer. When In installed the software the printer would not work on wifi. I mess around a bit and got the wireless part done and now the thing will scan but I get the add to the ADF. I don't know what that is. I have always used windows and it was so easy when it was working. just scan then a window would pop up I would have to change the name of the file but it was simple enough for me.😕 Any one else know what I mean? Thanks... Bud.... This is on a iMac 27 " 3.2 gig i5 core if that helps..