Gradients are created in the Shape Format dialog and adding additional color stops to a shape. These are all PowerPoint rectangles with 2-4 color stops added to the shape (with different colors, positions, angles, transparency and types).
The simple gradient is 2 stops where one side of the PowerPoint shape gets its color from one of the color stops and the other side of the PowerPoint shape gets its color from the second stop.
TIP: PowerPoint can have a maximum of 10 color stops.
Troy @ TLC