bonding

Directional means that the bond msut follow certain direction.

Ionic bond :
Consider a formula unit of NaCl, i.e. an Na+ ion and a Cl- ion. The nature of ionic bond is electrostatic attractions between the opposite ions, and the direction plays no role on such attractions. Therefore, ionic bond is non-directional.

Covalent bond :
For example, consider a CH4 molecule. The H atoms link with the central C atom with covalent bonds. The four covalent bonds must be tetrahedral in shape. If the H atoms are not placed tetrahedrally, no covalent bonds are formed. Therefore, covalent bond is said to be directional.