a.k.a chainsaw oil, chainsaw bar oil. An oil like all this other motor oils, but with additional “tackifiers” so it can stick to the bar while being flung around in open air (as opposed to gears and engines, which are, of course, sealed)

Kind of like how bar oil includes additives to stick, wd40 contains additives to penetrate and dilute - allowing grime to be removed. Good for rusty parts.

x and y are both viscosity ratings. The SAE rates how viscous an oil is, in a proprietary, evolving test. Whatever “10” corresponds to exactly, will not be explained by the first thousand pages of google results. (you'll have to read the engine's manual, or get an engineering degree.)

the “w” means “winter”…or maybe “warm”… anyway, 10W30 gets a 10 in winter conditions and 30 in warm.

yes, there is a difference: 2-stroke oil is meant to be mixed with the gasoline and combusted, 4-stroke isn't.