It's a term they've had to invent because the term "VPN" has been twisted into being synonymous with "proxy server" nowadays, but really a tailnet is a VPN (not a proxy!)

A tailnet is a true "virtual private network" in the sense that it's a non-physically defined network to which which numerous devices can connect and see each other directly. The underlying physical network, a layer below, is (mostly) irrelevant to the operation of this network, and that's the part that's beautiful about Tailscale's implementation in particular. You could have a Pi Zero in your garage, a VPS in Australia, and your laptop in New York all joining the same private network ('tailnet') and interact as if they were on the same local physical network (in most respects).

From a purely networking perspective, there are far better solutions than tailscale.

Have a look at full mesh VPNs like:

https://github.com/cjdelisle/cjdns

https://github.com/yggdrasil-network/yggdrasil-go

https://github.com/gsliepen/tinc

https://github.com/costela/wesher

These build actual mesh networks where every node is equal and can serve as a router for other nodes to resolve difficult network topologies (where some nodes might not be connected to the internet, but do have connections to other nodes with an internet connection — I work with networks like that every day).

Sending data through multiple routers is also possible. They also deal with nodes disappearing and change routes accordingly.

tailscale (and similar solutions like netbird) still use a bunch of "proxy servers" for that. You can set them up on intermediate nodes, but that have to be dealt with manually (and you get two kinds of nodes). You also have to create routes for the node to be able to access the control server.

Tailscalar here.

Tailscale traffic flows directly between your devices in every situation we can make it work. E2E encrypted packets are relayed by our proxies (DERP servers) only when we cannot make a direct connection. This is rare, currently less than 5% of bytes get relayed and we hope to keep pushing that number lower.

For more details see https://tailscale.com/blog/how-tailscale-works/

A tailnet is sometimes also called an 'overlay network'. The tailscale system sets up VPN links from all your devices to each other. This means they can act like they are all on one local network together, while not having to worry about the physical network setup the traffic is being carried on.

I was thinking about asking here if anyone could give a brief yet full overview of what exactly tailscale is and who/how it benefits. I've read about it, but I still don't get it.

Assume all your machines have Internet access, which they probably do these days. Instead of having to create firewall rules and routes and that whole mess in order to connect to a machine on "the inside" somewhere, the machine reaches out to the Internet and creates a tunnel, and you connect to the machine through that tunnel.

Isn't that a VPN?

Yes... but a painless and damn near zeroconf one. It's wireguard underneath.

i use it to access my NAS/network drive when im away from home.

when im at home i can access it no problem since im connected to my home network and so is the NAS. when im away its not possible to connect to it because im on a completely different network.

with tailscale installed on each device makes it seem like im still on my home network even when im away.

So its a bit like a VPN? Except that you can join specific devices from a multitude of networks?