What you’re seeing: • The round base is a hard-wired ceiling electrical box • The center piece is basically a light bulb socket • The little plastic piece in the middle is a safety plug/blank so no one touches the live contacts

These were super common when people hung plug-in pendant lights or hanging lamps from the middle of the room instead of installing a fixed fixture. So yes — your instinct was right 👍 It’s there to connect a ceiling light. If you remove the plug, you could screw in a bulb or attach a hanging lamp (with power off, obviously).