MultiBrush is a photo editing tool that lets you easily apply a series of effects to retouch your pictures using brushes to significantly improve how your pictures look.
There are two different toolbars available: a normal one and an artistic one. On the first one you can overexpose your pictures, use profiles, blur the image, and use the clone tool. On the second one you can find more simple tools, like the pencil, chalk, and eraser.
The program gives you lots of possibilities, like working with the layers system (which makes working a lot easier), and keeping a record of the changes you do, which can really come in handy in this type of programs.
MultiBrush is great for anyone who doesn't have that much knowledge about photography, since it lets you have pretty impressive results with barely any effort.