| Forgive my ignorance on "gearboxes".. is this an addition that some | motors have to run?
Gearboxes basically adjust the Kv rating of a motor (well, motor+gearbox) -- a 2:1 gearbox that slows the motor down by a factor of two also reduces the Kv rating by a similar amount. They generally allow you to swing a bigger prop more slowly, which is more efficient.
You can either design the motor to have a lower Kv rating, or use a gearbox to take a high Kv motor and reduce the value.
In general outrunners have lower Kv values than inrunners, but that's just a rough rule of thumb and there are many exceptions. It's all in how things are made ... | I'm guessing brushless doesnt require this
Brushed and brushless motors obey the same rules, they're just built differently. Both can use a gearbox or not.
| (actually.. i still dont know the mechanics of what makes a | brushless , brushless, vs brushed etc).. I'm assuming it has | something to do with the inner parts
Brushless motors tend to be somewhat more efficient when you have a motor that often runs at speeds less than full power. In the case of models, they tend to be compared to cheap, poorly made can motors and so they have a reputation of just being a whole lot better -- but if you compare against good quality brushed motors, the difference becomes much smaller.