The harvest is the time when you reap what you sow. As a verb, to harvest something means that you pick or gather it. You might harvest your sweet corn late in the summer.
As a noun, harvest means the time of year when crops are ripe and ready to be gathered. The picked crop is also called a harvest: a bumper crop is a plentiful harvest, and a poor harvest is when things didn’t grow as well as expected. As a verb, to harvest something is to gather, trap, or cull it. You can harvest a soybean crop, you can harvest beaver pelts, or you can harvest tissues or organs for transplants.