Hi
Get Started refers actually current sprint and backlog actually refers as a Future sprint work.
For Example,
We are going to create a One user story which needs to be addressed immediately. So we can create that user story under Get Started section. Then we can move those user story to exact sprint
We are going to create a One user story which needs to be addressed later. So we can create that user story under Backlog section
Hi Chihiro,
Following documentation will explain you the importance of Sprint. It is one of Agile Practice.