Difference between Covalent Compounds and Binary Covalent Compounds?

Covalent compounds can contain several different elements.

Examples are H₂SO₄, POCl₃, and CH₃COOH. Each of these contains three different elements.

Binary covalent compounds are a subset of covalent compounds. They can contain only two elements.

Examples are H₂O, N₂O₅, SF₆, IF₇ and P₄O₁₀.

Note: It's the number of elements, not the number of atoms, that tells you if a covalent compound is binary.