How does the weather software that comes with Apple's mobile phone set the geographical location?

Setting the weather software attached to the mobile phone can:

1, directly use the mobile phone location service to locate the weather information of the city where the mobile phone is located.

Open the weather location service in Settings → Privacy → Location Service.

2. Search city weather information. Open the weather software, and there are three banners in the lower right corner of the home page. After clicking, the following figure appears:

Click+in the lower right corner to add a city, and you can see the weather information of this city.