Most of people think socks machines are similar to knitwear machines, but it's not actually true. Socks machines have the needles disposed in a circle, making up a kind of cylinder.
There are mono and double cylinder machines. Double cylinders are the ones able to knit jacquard patterns, while mono cylinder usually make only embroidered socks. Both are able to produce plain colour socks.
More needles the machines have, more fine is the knitting and of course finest has to be the yarn used.
Attached an image of the needles cylinder.