Swap usage in web hosting refers to the use of a swap space, a portion of a hard drive used as virtual memory when the physical RAM is fully utilized. When a system runs out of RAM, less frequently used data is moved to the swap space, allowing more critical operations to continue using the RAM. Swap usage is crucial for preventing system crashes in scenarios of high memory demand, but it's slower than RAM. Monitoring swap usage helps in assessing whether a server needs more RAM based on its workload and performance.
