why do you need to know mate i don't mean to sound harsh but if you knew much about the engine it would be self explanetary.
all these bearing are not normal bearings as i believe you would think, they are flat circles of multi compound soft metals to create a surface that won't damage the moving parts under load, and wears out according.
the connecting rod bearing wraps around the crank and then has the con rod bolted around it, also known as the big end bearing, and the little end bearing is at the top of the con rod holding the piston in place, and is incorperated into the con rod and hole unit needs replacing.
a main bearing i believe is the bearing the goes onto the centers of the crankshaft and is held on with metal caps to the block, i also thought this was a crankshaft bearing but could mean the bearings on the end of each side of the crank.