All Mac OS X users have a basic text tool, but not a drawing tool. Paintbrush is an application that comes to fill that role, similar to Windows Paint.
Paintbrush is a program that basically works like you used to in MacPaint. It is a simple program that quickly allows you to create drawings with basic, but necessary tools such as brush, eraser, clip, airbrush, and some figures such as zoom, circles and rectangles.
The program can open and save images in different formats such as BMP, PNG, JPEG, TIFF and GIF. Paintbrush is a free program and allows you to open a lot of pictures of common applications for Macs.