What is “Low Data Mode” on my iPad’s connection to my iPhone as hotspot?

According to this source Apple introduced a new feature to reduce and limit cellular and Wi-Fi usage. This feature is called Low Data Mode. You can use this feature on your iPhone, iPad or iPod touch to limit the mobile data used in background mode by apps.

Different apps use different ways of reducing data usage in Low Data Mode. In general, here's what you can expect:

Apps might stop using network data when you're not actively using them.

Background App Refresh is turned off.

The quality of streaming content might be reduced.

Automatic downloads and backups are turned off.

Services such as iCloud Photos pause updates.

Built-in iOS apps and services adapt to Low Data Mode in the following ways: App Store: Video autoplay, automatic updates, and automatic downloads are turned off.

Music: Automatic downloads and high quality streaming are turned off.

Podcasts: The frequency of feed updates is limited, and episodes are downloaded only on Wi-Fi.

News: Article prefetching is turned off.

iCloud: Updates are paused, and automatic backups and iCloud Photos updates are turned off. FaceTime: Video bitrate is optimized for lower bandwidth.

See Apple support page, Use Low Data Mode on iPhone, iPad, and iPod touch.

Please note that Low Data Mode is automatically enabled when you are connected to a Personal Hotspot.