Apple Watch- Cellular

If you have an iPhone 6s, SE, 7 or newer, the Series 3 will pair with your iPhone.

If you have a GPS only Apple Watch, it will do Everything the cellular model will do as long as you have your iPhone nearby.

If you get a cellular Apple Watch, and activate the cellular with a carrier that support the Apple Watch (see below), then the Apple Watch will share your iPhone's phone number, and your carrier will charge you a monthly fee. In the U.S. it is $10 per month to share your iPhone's phone number.

Cellular Carriers that support the Apple Watch, which models, the radio frequencies each model uses, and the country where they offer service:

https://www.apple.com/watch/cellular

You can use your apple watch to make calls and send texts as long as your phone is within bluetooth range of your watch.