For some background information, a covalent bond is a bond in which two or more elements SHARE electrons to become stable. In retrospect, ionic compounds TRANSFER electrons to make ions and become stable.
Covalent formulas or covalent molecules are compounds that only (for simplicity) contain NON-METALS.
For example, potassium chloride, KCl NOT covalent as it contains a metal. However, if you were to analyse something like NO2, this IS covalent as it contains two non metals.