There are two main types of software: system software and application software. System software includes operating systems like Microsoft Windows, which provides a graphical user interface and allows users to easily access and switch between programs. Application software is used to perform specific tasks and can be custom software made for large organizations or commercial software packages for personal use, like programs for writing, calculations, and games. Instructional software is a type of application software designed specifically for teaching and self-instruction, and includes tools like drill-and-practice, tutorials, simulations, and instructional games. Teachers must carefully evaluate instructional resources to ensure they are accurate, unbiased, and effectively help students meet learning objectives.