More than just the expected pencil and color pallete, the program also has other tools, like the rubber stamp, that allows the use of many figures, like penguins, numbers and math symbols, so the kid can stamp them in the picture. Basic shapes like squares and rectangles can even be turned before inserting them in the image. Special (magic) effects can also be added to image, like for example, brick effect, chalk, fading, blur, mirror and flip. The effects can be accessed from the "magic" button. There is also a line tool that, like the pencil, can have the format (shape) choosen by the kid.
Since one of the strong points of Linux is security, this software couldn't be different. Imagine the damage your 6 or 7 year old kid would do, having access toyour files in the OPEN/SAVE dialog box. With this situation in mind, Tux Paint deals with files in a different way. When you click in SAVE button, no dialog boxis opened. When opening a file, the kid sees only the thumbnails of saved images,having no access to other files in directory or system. This is not only safer, but also easier for the child to work with the software.
[Thanks to Daniel José Viana <firstname.lastname@example.org> for the translation.]