It's a lightweight machine made by Singer from 1936 (or thereabouts) thru the 50s. It will never say "featherweight" on the machine itself as it's name was actually 221 model. Made or aluminimum, it weighs about 11lbs, comes in a black tolex covered case that looks like an old record case (45rpms). The machine has a fold-up extension bed. Came originally in the black japanned finish but was later made in tan and also in what Singer called "bisque" but in fact ranges from white to mint or celery green. They also had a rare issue of crinkle or godzilla finished machines from the war years. And, Singer also came out later with a free-arm version (I think in 1951 but not absolutely sure of that date). They are a simple mechanical machine that does only a straight stitch and reverse stitch, no fancy or decorative stitches. Most of us featherphiles can at least do routine maintenance on our machines and some even restore them.
Much later in the 80's Singer made and sold a cheap, plastic machine that they did call a featherweight. For the most part it was a piece of junk. There was also a knock off machine sold in the 90's called an alphasew. It looked like the original 221 but was also junk.
Beware...featherweights can be addictive...like Lays potato chips, ya can't have just one!