The primary functions of a computer's RAM (Random Access Memory) include temporarily storing data for active applications and providing fast access to the CPU. RAM allows systems to quickly read and write data, facilitating smooth operation and multitasking. It is crucial for executing programs, buffering data, and caching frequently accessed information to improve performance. The amount of RAM in a computer directly affects its ability to handle multiple tasks and operate resource-intensive applications, making it a vital component for overall computing efficiency.