The problem it solves
Every time you open a website, two parties learn something. Whoever runs your network — your broadband provider, the café, the hotel, the airport — sees which sites you connect to and when. And the site itself sees your IP address, which is usually accurate to the city, sometimes only to the region, and occasionally wrong by a whole country.
Neither of them asked your permission. Both of them keep records. In several countries, your provider is required to.
What a VPN changes
A VPN puts an encrypted tunnel between your device and a server you choose. Your provider can see that you're connected to Sable and how much data you're moving, but not what's inside it or where it's going. The sites you visit see the server's address instead of yours.
That's the whole mechanism. Everything else is detail.
What it does not do
It does not make you anonymous. If you sign in to an account, that account knows it's you — a VPN cannot undo that, and no honest provider claims it can.
It does not stop tracking that follows you through cookies and browser fingerprints. Use browser settings and content blockers for that; the two tools solve different problems.
It does not protect a device that is already compromised. If something is running on your machine that shouldn't be, encrypting its traffic just gives it a private line.
And it does not hide your traffic from the VPN itself. Whatever a site has not already encrypted is readable at the exit server. That is true of every VPN ever built; the only question worth asking is whether the company writes it down. We do not, and the logging policy says so in detail.
When it is worth paying for
It's worth it if you use networks you don't control — hotels, airports, shared offices, rentals. It's worth it if your broadband provider sells browsing data, which is legal in more places than most people realise. It's worth it if you travel and want your home services to keep working.
It's less useful if you're at home on a connection you trust, browsing sites you'd be happy to name out loud. That's an honest answer, and it costs us sales to give it.
How to judge a VPN service
Read the logging policy before the feature list. If it says “no logs” without saying what that covers, it means nothing — every service keeps something to run at all. The question is what, and for how long.
Check where the company is. Check whether cancelling takes one click or five screens. Check whether the apps contain third-party trackers, which several well-known VPNs do.
Then assume the answer to “can I verify this myself?” is usually no, and choose the service whose written promises are narrow enough to be keepable.