what is a degause button on a tv?

Answer 1

If your TV has a degauss button (pretty rare nowadays, as degauss is usually automatic) it is used to demagnetize any metal parts in the TV that may have somehow gotten magnetized. The magnetic field from those magnetized parts can create discoloration in areas of the picture (usually near the edges or corner of the picture). The degauss button energizes a coil of wire around the picture tube with AC current which gradually decays, demagnetizing any magnetized parts. (Gauss = unit of magnetic field strength).

Answer 2

There is no degauss button on a TV, but there is usually one on your computer monitor.