A service like Nord VPN or other such VPN providers setup a connection between your device and an exit point that they manage (a server to keep things in a client-server structure). So the idea there is that no one monitoring your traffic should ideally see what websites you visit, what things you download or what devices you connect to (I'm keeping this broad and very surface level to be able to reach a common point of understanding and if anyone adds to this, by all means, let's clarify this as it's quite a complex topic).

So let's say the local government blocks access to certain content, you can connect to a VPN provider's network, select an exit point (a server) and your traffic is routed through them. But this can be monitored by that provider and I read an article recently that highlighted a lot of free VPN providers cannot be tracked down to companies, so you couldn't say who is running those servers. Which means, you don't know if all your traffic isn't actually recorded in the end and sold on to someone.

This brings me to the first difference - you can setup your own server (at home or more likely through an infrastructure as a service provider like Hetzner, Ovh, DigitalOcean, etc) and install Tailscale on it and on your device(s). This way your connection is secured to the server and the server is the exit point now. Your provider in this case, cannot see what your server is serving you. The added control here is that the server IS YOURS, so you can clear logs, take it down and setup another one and so on.

The second difference is that a VPN in most canonical cases has a client-server construction. But this means that there is a hierarchy and that all your devices use that server as a gateway of sorts. If I understand it correctly, Tailscale acts as a mesh that is laid on top of your existing connections, but it means that devices that you connect to the same mesh, behave as if they were on the same LAN network, but over the internet. So let's say you're on holiday, you can connect to your home computer (assuming your device and your home system have Tailscale, an internet connection and are running ofc) as if it was on the same network. Because it is. It's on a virtual network where Tailscale creates these connections and manages the IPs on the network. So you can view your movies, copy over your pictures from your phone to your home computer and so on.

You could also maybe have a home server which might be running a number of services. Enabling SSH over the internet has it's risks, but Tailscale could alleviate a lot of these risks because you would have a fixed IP on this virtual network and so does your server. So suddenly, you can define a rule on your server firewall that says "hey, block everyone, except THIS ip".

Lastly, you could maybe even just share pictures, documents and whatever else with friends, family or anyone else who is running on the same Tailscale network.

I really hope I haven't completely misunderstood the service and I'd be happy to get more clarity or some better examples. These are SOME of the use cases I can think of, but there are probably more! Btw, I don't use Tailscale, I am considering it after having considered other mesh networks like Yggdrasil as that's the part I'd be interested in...