Prior to iOS 15, FaceTime has only been available for use between Apple devices (iPhones, iPads, and Mac computers). If you wanted to video chat with someone with a non-Apple device such as an Android or Windows smartphone, you needed to use a third-party video chat app such as Zoom.
With iOS 15, Apple added the capability to FaceTime non-Apple smartphone users.
FaceTime an Android or Windows Smartphone User
1. Open the FaceTime App and tap New FaceTime.
2. Enter the name of the contact to invite in the To: field.
3. When a non-Apple contact is invited, a green Invite with Messages button will appear just above the keyboard.
4. Tap the Invite with Messages button to open a message to the recipient.
5. Edit the default message text if you want, then tap the send button. This sends the FaceTime invitation to the recipient.
Once the FaceTime invitation has been sent, an active FaceTime call will begin and you will wait for the recipient to join.
You can FaceTime with multiple people by adding all the contacts in the To: field when creating a new FaceTime call.