The Dodge/Burn tool in GIMP is a paint tool that lightens or darkens colors in an image.
Steps to use the Dodge/ Burn tool are:
• To activate the tool from the image-menu: Go to Tools > Paint Tools > Dodge/ Burn, or by clicking the tool icon 
, or by using the Shift + D keyboard shortcut.
• Select the brush style and size from the Tools Options pane.
• Move over the area that you want to brighten by holding down the left mouse button.
