Step-by-step explanation:
A chemical bond that is formed due to sharing of one or more number of electrons between two neutral atoms is known as a covalent bond.
For example, CO is a covalent compound as there occurs sharing of electrons between carbon atom and oxygen atom.
On the other hand, a bond that is formed between two neutral atoms due to transfer of one or more number of electrons is known as an ionic bond.
For example, KCl is an ionic compound because sharing of electrons take place between potassium and chlorine.
Thus, we can conclude that when one or more pairs of valence electrons are shared by two neutral atoms, then covalent bond is formed.