It’s a little piece of paper (or a digital code) that helps pay for your glasses or contact lenses. You don’t have to be on benefits to get one, but it helps if you qualify through certain criteria. It’s not a loan—it’s a straight-up contribution towards better vision.
Imagine you’re at the cinema, and someone hands you a free popcorn voucher. That’s basically this, but for seeing clearly instead of snacking. Your eyes will thank you, and your wallet will breathe a sigh of relief.