It is more like putting your finger over the intake. It sucks fuel into the carburetor. The smaller the venturi size of your intake, the more fuel draw the carb will have. Fully closed off (or mostly) sucks up fuel optimally.

I will go through my starting procedure for a gasser.

Full throttle
closed choke
ignition on
rock prop back and forth 7-8 times (gets pump pumping fuel)
Flip prop through compression hard and fast, usually 3 -5 times, until engine fires, then it will die. Now you have fuel all the way up.
Open choke
Lower throttle to high idle.
Flip prop hard and fast, should be running within 3 flips.

The engine will not continue to run if the choke is closed. I highly recommend looking into adding one, and hopefully there is something available for your engine. On one of my old gasser carbs that had no choke, I put a cork (from a tequilla bottle) on a music wire linkage, and choked with that. It worked great.