The document is a letter from a math teacher encouraging a student to take AP Computer Science based on their success in math. It details that AP Computer Science covers topics equivalent to a semester of college computer science, uses Java programming and Linux, and may provide college credit depending on exam scores. The teacher believes the student's math background will help them enjoy learning new computer science concepts like algorithms, data structures, and programming. Students are asked to fill out a form to select AP Computer Science for their course schedule.