I suggest you try google and then ask questions on this site. I'm sorry to sound harsh but this is a very basic question that you could have looked up with a little effort (very little) rather than posting it here. If you still aren't clear on something by all means ask that but show us you have done some basic looking and thinking first.
There are two categories of chokes to reduce pressure. One is a fixed choke. The other is a variable choke.
The fixed choke works like a restriction orifice except that it can handle lots of pressure drop for extended periods. Old designs from the 1930's exist all over the world. The replaceable bean (bored tube that threads into the body). With the standard designs you can get the beans from supply houses in any oil-patch supply. These are sized for the specific condidions; or replaced by trial and error.
The variable choke has a valve plug that is adjustable within the restriction. These are sized to permit design flow at about 50% travel so that you can accommodate changes.
I find that Cor-Val in Houma, LA are quite competitive compared to the typical suppliers.
