Which way should the teeth on a chainsaw face?

A chainsaw's chain should be fitted so that the points of the teeth face in the same direction as the chain moves. Then they will cut into the wood without needing much downward pressure.

If the teeth are sharp you should never have to force the chain down into the surface of the wood.

If you find you have to force the chain down to make it cut the wood then the teeth must either have gone blunt - and the chain needs to be sharpened or replaced - or the chain was installed with the teeth facing the wrong way so that the backs of the teeth just rub over the surface of the wood and you need to press down very hard just to get the teeth to wear down into the wood instead of cutting it cleanly.