It's like a Gift Card in the App Store or Steam, or that secret cheat code from games.
Usually services try to bind your card and charge money every month. We don't do that. You simply buy a unique code (key), enter it in the field — and days of access are instantly added to your account.
The key doesn't expire, you can gift it to a friend or activate it yourself when you need the internet most. Full
control, no auto-renewal, and no extra data.