Sewing machines have evolved a great deal over the years. The first machines were treadle sewing machines that didn't require any electricity at all. Eventually, they figured out a way to put an electric motor on a treadle machine as an add-on.
As soon as they figured this out, they began to produce machines with the electric motor built into them. These are what we refer to as a manual or mechanical sewing machine. Although it does have an electric motor, it doesn't have electronic components within it to automate any processes. You have dials for making variable choices and push buttons to turn things on or off.
The more modern machines are considered electronic or computerized. They have digital displays and touch screens on them. There are many functions that they will perform without requiring a dial or button.
This video is about a manual machine that I inherited from my mother. It is a 1961 Necchi made in Italy. It's one of the best manual machines ever built. I'm very impressed by this machine and quit using my electronic machines after I got it.
Just because they aren't new, doesn't mean these machines have no value. In many cases, they are more reliable and sturdy than anything you can buy in today's marketplace. I think you'll be surprised at some the things you can do with these machines. Mine has cams that allow me to make more stitch variations than almost any computerized machine on the market.
Watch the video to learn how a manual sewing machine works.