what is the difference between coordinate and covalent bonding?

A covalent bond is formed by sharing of electrons ex. in a molecule of nitrogen two atoms are bonded covalently ( at. no. of N₂ is 7 so it contains 3 electrons in 2p shell it needs 3 electrons to complete its octet so in a molecule of nitrogen both atoms contribute 3 electrons which are then shared by both and thus they attain nearest nobel gas configuration).

 

In a Coordinate bond both atoms contribute equal no. of electrons but they are not shared ex. HCl In hydrochloric acid both hydrogen and chlorine contribute one  electron to the bond but chlorine being more electronegative than hydrogen  exerts attracts the electron pair towards itself.