Complete hobbyist here. I have two questions I have a problem figuring out. I have hard time finding information about axis and types of connections they have. For example take this worm gear reducer:
It has axis connection with small extrusion on one side, where motors usually have shaft with one flat side. I found this adapter :
on the site it's called Axle sleeve but I haven't found this part by this name elsewhere, so maybe there is another more precise term?
Is there a beginner friendly resource I can study to get more familiar with this system? What both types of connections are called etc.

