The Blur and Sharpen Tools allow us to manipulate edges by making them softer or harder. They do exactly what you would expect them to do; blur and sharpen.
Both tools have similar attributes such as Strength (increase or decrease the strength of the tool, or how much it will blur) and the brush, all of which can be adjusted in the Options Bar for each tool. To use the blur or sharpen tool, simply set up the brush to your specification, hold down the mouse button, and hover over the areas you’d like to alter in your image.
You should have a pretty good feel of the basic retouching tools by now. The next step in mastering Photoshop is usually learning how to use the painting tools to compliment your photo remastering abilities!