A choke is a constant flow device used at the top of a well to control it. Provided the choke is correctly sized (ie flow through the choke is in the critical flow region), regardless of pressure changes downstream, the same flow will come out of the well. So the well is controlled. They come in all sorts of varities: fixed, adjustable, welded, flanged, surface, subsea.....
Manufactuers include:
Anson,
Willis,
Masterflo,
So looking at the websites for these companies should tell you everything you may want to know.