Locate your key ring. (Possibly easier said than done.)
Remove any keys from your key ring that you don’t know what they open.
Place these unfamiliar keys in either an envelope or sandwich bag, labeled, “Keys to Something,” and save them, just incase one day you realize what they’re for.
You can go around your house looking for all of your “keys to something.” I happened to find some in a kitchen drawer, a few in my desk drawer and even one in the linen closet.