i have 2 questions.. 1. is the earth's mantle heated evenly, and 2: what is convection?

Answer 1

1. No, there are currents that flow throughout.

2. Convection is the transferrence of heat.

Answer 2

The upper mantle ranges in temperature between 500-900 deg C while the lower mantle can get as high as 4000 deg C. It is solid so I would expect there would be some limited variation.

Convection is the internal movement of currents within fluids (this can be either gases or liquids). It does not necessarily have anything to do with heat transfer.