Is the Apple Watch 7 charger different from previous chargers?

Yes, the charger you will receive with your Apple Watch 7 is designed for fast charging, when you use it with a 20W USB C charging brick. The charger is supplied. The charging brick is not. It is the same size as previous chargers, but internally it can charge your watch faster and instead of a standard USB A connector, it is now USB C.

That said, if you have a previous Apple Watch and a charger for it, you can still use that charger, it just will charge at the same pace as it always did.

I believe it is similar, but I understand it is supposed to be a USB-C connector. It is a fast charger, which is not supported on other series watches. What I mean is that fast charging is not supported on other watches. The new charging puck will work with other series watches though, as well as the older pucks will charge the Watch 7, just not fast charge it.