The knee on neck/throat choke is a controversial choke in BJJ as you are basically putting your knee on your opponent’s neck which can seem quite brutal.
Nevertheless, it is a very effective submission. You can also use on a opponent that is very defensive, by alternating from knee on belly to knee on neck until they give you something such as an arm….
BJJ black belt Jena Bishop provides some insight on making the knee on neck choke work along with a transition to armbar:
Here is another interesting option:
Here is Cyborg doing the knee on neck in competition: