The type of computer memory that is volatile and primarily used for temporary data storage is RAM (Random Access Memory). It stores data and machine code currently being used by the CPU during operation. RAM is fast and allows quick read and write access, making it essential for performance. However, because it loses its content when the power is turned off, it is crucial for temporary applications while a computer is running, distinguishing it from non-volatile memory like hard drives or SSDs, which retain data without power.