Distinguish between speed and velocity.

Sometimes they are the same in physics. it depends how the question is worded but speed comes before velocity. If you take the derivative of speed you will end up with its velocity. The same goes when you take the integral of velocity.

The most simple difference between velocity and speed is: velocity has both magnitude and direction, while speed only contains magnitude. Hope that helps you.

What is the things about?

Work is reduced while time is decreased