From Test-Scratch-Wiki
Motor blocks are used to control the motor in the LEGO WeDo Construction Set.
Making the Motor Blocks Visible
The motor blocks are in different categories in Scratch 1.4 and 2.0. You need to choose them, they are not visible by default.
To make the motor blocks visible in: 2.0: Go to "More Blocks", click "Add an Extension", then choose "LEGO WeDo."
1.4: Click "Show Motor Blocks" in the Edit tab. They can be then found below within the Motion palette.
The motor blocks can only be used with a LEGO WeDo Construction Set, but can still be viewed without one.
Blocks
Scratch 1.4 has the following five Motor blocks:
For the Scratch 2.0 motor blocks, see LEGO WeDo Construction Set