Cellular on Apple Watch Series 3 is for when you’re disconnected from your iPhone. With just your Apple Watch, you can make and receive calls, text messages (including iMessages), use apps, GPS, and do many of the things you can with your iPhone, except without being connected to it. It’s great for when you, say, leave your iPhone at home, or your iPhone’s battery dies, or you just want to be “disconnected” from your phone for a while. I think more than anything, cellular on Apple Watch is a symbol of a growing importance of the role of the Apple Watch in daily life. I don’t think it’s going to eclipse the iPhone or smartphones in general any time soon, and I don’t think that is Apple’s intention. But Apple Watch is transforming what you can do when you don’t have access to your smartphone, and helping the Watch become yet another essential Apple product that you cannot live without.