How does earned value give a clearer picture of project schedule and cost status than a simple plan versus actual system

How does earned value give a clearer picture of project schedule and cost status than a simple plan versus actual system?

2. How does earned value give a clearer picture of project schedule and cost status than a simple plan versus actual system?

 

3. Schedule variance (SV) is in dollars and does not directly represent time. Why is it still useful?