Tux Paint is meant to be a simple drawing program for young children. It is not meant as a general-purpose drawing tool. It is meant to be fun and easy to use. Sound effects and a cartoon character help let the user know what's going on, and keeps them entertained. There are also extra-large cartoon-style mouse pointer shapes.
Tux Paint is extensible. Brushes and "rubber stamp" shapes can be dropped in and pulled out. For example, a teacher can drop in a collection of animal shapes and ask their students to draw an ecosystem. Each shape can have a sound which is played, and textual facts which are displayed, when the child selects the shape.
Tux Paint is portable among various computer platforms: Windows, Macintosh, Linux, etc. The interface looks the same among them all. Tux Paint runs suitably well on older systems (like a Pentium 133), and can be built to run better on slow systems.