what is element?

Solution-

An element is a pure substance which consists of only one type of particles. These particles can be atoms or molecules. For example Carbon is made up of only carbon atoms, gold is made up of only gold atoms, Hydrogen gas consists of Hydrogen molecules (formed from two atoms of Hydrogen) etc.

There are various element each of which have few roles, example-

Carbon-all living things have carbon.They help keep us alive.
Hydrogen-it is in the sun so that it helps warm the Earth.