The Gradient tool creates a gradual blend between colors using preset or custom gradient fills.
Photoshop Gradient Tool
  1. Make a selection around the area you want to fill with a gradient.

  2. Select the Gradient tool (G) .    

  3. Use the Options bar to customize tool settings, like Gradient Type and Opacity, to get the effect you want.    

  4. Drag the cursor across the selected area to fill it with a gradient.