Ok, you got me. It’s a juicer. What a gadget!
You slice off the top of the core of your chosen fruit with a sharp knife, then just screw in the juicer. You hold the lemon (said chosen fruit) upright and gently squeeze, the little cup on top fills up with juice, voila. Once you’ve got enough you can put the lemon in the fridge for another day without fear of it going all wrinkly ‘cos you haven’t cut it in half. Flippin’ fantastic.