it forms between two non-metallic atoms. However, covalent bond is divided into two types: the polar covalent bond in which electronegativity difference is greater than 0.4 but lesser than 1.9. Some examples include carbon dioxide and methane. Another type is the non-polar covalent bond in which the electronegativity difference is lesser than 0.4, some examples include oxygen gas (two oxygen atoms).
hope i helped you. :*