What does the term ''Best-corrected vision'' mean in eyesight

It means to be best corrected vision that can be done with lenses. If u have an uncorrected visual acuity that means without glasses or contacts. A corrected visual acuity is with glasses or contacts. Not everyone can be corrected to 100% of their potential with glasses or contacts. So lets say u had an uncorrected visual acuity of 20/400 in ur right eye, & they put glasses on u that should correct ur refractive error, but u have some sort of issue with ur eye health like macular degeneration, or something else & u can only be brought up to 20/200, then ur ''best-corrected acuity'' would be 20/200, & that is with glasses or contacts. Get it?

meaning the best degree that u can have to correct ur error