A tiny little command console thing. You need to discover "secrets", which are obtained by typing certain commands into the console. Press space to activate the console, and type "hint" for a hint. There are currently eleven secrets in total. All secrets lack spaces.
I thought of this myself, with slight inspiration from the various Geometry Dash "vaults", where you enter codes into a textbox and you can also find secrets, though the secrets there actually can affect the game. But there isn't any game here, so secrets are just a number recorded in a variable. Did you know: The cat's favourite food is tomato sauce and chicken.