Bolt and Screw are two examples of fasteners. Both devices are used to fasten metal bodies or objects together. Although both materials are used majorly for the same reason, there are some differences between them. Bolt is a type of fastener that has a cylindrical body that is threaded, and it has a larger head on one end so that it can perfectly fit an unthreaded hole up to the head when inserted. A bolt doesn't need to be turned so that it can be tightened when you are inserting it into a hole.
A screw, on the other hand, is a metal fastener which consists of a shank, partially or completely threaded shank, sometimes with a threaded point, and ahead used to both hold the top material and to drive the Screw either directly into a soft material or into a prepared hole. A screw needs to be tightened by turning it in a clockwise direction.