CG 20 10 is the ISO form that grants additional insured status for ongoing operations, the work a sub is actively performing. It is the workhorse endorsement GCs ask for at the start of a project.
On its own, CG 20 10 does not cover completed operations, claims that arise after the work is done. That is why GCs often pair it with a CG 20 37, especially on projects where latent defects could surface later.