Restored is the equivalent to a frame off restoration on a car. Every part would need to tumbled, cleaned etc. If decals are worn new would be applied. NOS or replacment playfield installed. If theres damage to cabinet its repaired. Basically everything looks new. Doing a portion of the items above, such as "just" a playfield swap, can mean a game is partially restored.
Many sellers are now listing games as restored that are really just shopped. Shopped means taking an original game that has been played regularly over its lifetime and cleaning it. Cleaning a game does not mean its restored.