What is the dodge tool in Adobe Photoshop?

Answer 1

First select it from Toolbox then look at options bar (below menus) and set options for this tool, adjust brush size (when using Dodge tool you are actually paint with Brush) click and paint directly on image.

Answer 2

The dodge tool lightens an area of an image, while the burn tool darkens an area of the image. These tools come in handy for controlling exposure on specific areas of a print.

Answer 3

Dodge and Burn tools are regulating Exposure on specific part of image (part which you will paint with this tools). Dodge will lighten and Burn will darken painted pixels on image.