# Phosphates Functional Group

In my text book it states that a phosphate group is considered to be $\ce{-OPO3^{2-}}$. However, online it states that phosphate is $\ce{PO4^{3-}}$. Why do these contradict? Am i confusing phosphate the chemical with the phosphate group? Please see image for reference.

Phosphate $\ce{PO4^3-}$ is an anion of the phosphoric acid $\ce{H3PO4}$. Term phosphate comes from a salt, for instance a sodium phosphate $\ce{Na3PO4}$. $\ce{Na+}$ are bound with a $\ce{PO4^3-}$ through ionic bonds. No electron sharing.

To annotate specific moieties of a molecule skeleton, a chemical group term is used. The phosphate has donated one pair of electrons on the oxygen to have a covalent bond with other molecule, for instance sugar in the image, and becomes a phosphate group in the molecule. Since the electron pair does not sit on the oxygen any more, but is shared with carbon, the phosphate charge is lowered to −2.