The function of an SSD (Solid State Drive) in a computer system is to provide fast and reliable data storage. Unlike traditional hard drives, SSDs use flash memory to store data, which allows for quicker data retrieval and higher performance. This results in faster boot times, shorter loading periods for applications, and improved overall system responsiveness. Additionally, since SSDs have no moving parts, they tend to be more durable and energy-efficient, making them a preferred choice for modern computers.