Scilab is an open-source numeric computing software package that is similar to Matlab. It allows matrix manipulations, plotting, animation, and other tasks. While Scilab has advantages like being free and including tools like Xcos, it also has disadvantages such as slower execution speed compared to Matlab, poor documentation, and a tendency to crash or lock up. The document discusses both advantages and disadvantages of using Scilab compared to commercial alternatives like Matlab. It aims to provide an introduction to Scilab for new users.