https://www.bleepingcomputer.com/news/microsoft/microsoft-edges-new-feature-will-reduce-memory-and-cpu-usage/

To improve memory and CPU usage in Edge, Microsoft is working on a new feature called "Sleeping Tabs".

Sleeping Tabs feature is based on Chromium's freezing technology that basically pauses a tab's background activities (such as advertisements, javascript, script timers, etc) to minimize resource usage.