Hipster jokes at the ready...

[Mr. President]

And what differentiates a cog from a sprocket from a gear?

Well you see latch they are all toothed wheels. Gears are designed to mesh with other gears, and the geometry of the teeth is optimized for this purpose.
Sprockets are designed to drive, or be driven by, a chain (such as in a bicycle) so its teeth are shaped for that purpose (pointier than gear teeth). A cog -- or more properly, a cogwheel -- as I understand the term, has squared-off teeth designed for a different kind of mechanism.

I hope that's right latch i just kinda winged it of the top of my head!

LOL

Okay and no more ?'s now!!!!!!