What is live server?
It is fronted preview with hot reload on save.
Why is this helpful?
Lot of developers have lot of screen estate so they can have edior and fronted opened in same time. Now if you want use full advatage of that you need manually reload fronted window after every save. This can be frustrating doing whole day and should be automated.
What this feature is doing?
This feature is performing auto-reload of fronted preview with every save. So when changes are made and ready on frontend it will reload fronted.