The Cashew tree is a tropical tree, native to Brazil, the Portuguese took it to plant in India where they spread through SE Asia and eventually Africa. It grows very easily.
An edible apple fruit develops from the receptacle of the cashew flower, it’s high in vitamin C, (my children weren’t fond of it but the locals have the apple and discard the nut). The cashew nut is inside a kidney shaped shell attached to the bottom of the apple. There is a caustic liquid inside the shell that can cause severe burns so careful when handling.
Shelling the nuts is a difficult process: Freezing the shells and then separating the shell from the nut before it thaws is one way to remove the nut, but gloves, long clothes and safety glasses need to be used. Another way is to heat oil to 210 degrees celsius and drop the nuts for 2 minutes, cool in a bucket of water and shell them. Roasting the nuts for a minute in a fire and then place the nuts into something absorbent to remove the last caustic liquid.