If your watch is connected to Wi-Fi or cellular
When your iPhone is off or out of range, your Apple Watch can use a Wi-Fi network to send and receive data. And if your watch is equipped with cellular, it can connect to a cellular network.
If your Apple Watch is connected to Wi-Fi, the Wi-Fi icon 
appears in Control Center. If it's connected to cellular, the cellular icon 
appears. Learn how to set up cellular.
A Wi-Fi or cellular connection lets your Apple Watch do the following things—even if your iPhone isn't with you.1
Use Siri to get directions, send iMessages, and more.
If you can't connect to Wi-Fi, cellular, or your iPhone
When your Apple Watch is disconnected—for example, if you're hiking in an area without Wi-Fi or cellular signal, or your iPhone is off—you can still do these things.
Display photos from synced photo albums.
Play music, podcasts, or audiobooks that you've synced to your watch.
Make purchases with Apple Pay.
Record thoughts and ideas.
Not all features are available on all Apple Watch models.
1. To receive SMS, MMS, or push notifications from third-party apps on your cellular Apple Watch, your paired iPhone must be powered on and connected to Wi-Fi or cellular, but it doesn't need to be nearby. You also need to be signed in to iMessage on your iPhone.
2. If you're on Wi-Fi and want to call a phone number, make sure that Wi-Fi calling is turned on for your Apple Watch. Otherwise, try making a FaceTime audio call.
3. Streaming music and podcasts is available on Apple Watch Series 3 and later.
4. For GPS accuracy when you walk, run, or cycle outdoors, select the appropriate Workout and bring your iPhone. For GPS accuracy, you can also calibrate your Apple Watch. Apple Watch Series 2 and later has built-in GPS that allows you to get more accurate distance and speed information during an outdoor workout without your paired iPhone.
5. The Compass app is available only on Apple Watch Series 5.