Swap space is a portion of the hard disk that is used as virtual memory by the Linux operating system. It is used when the physical memory (RAM) of the system is full. Swap space can be used to improve the performance of the system by allowing it to store data that is not currently being used in RAM.
There are a few different ways to check the swap space usage on a Linux system. One way is to use the `free` command. The `free` command will display the amount of total swap space, the amount of swap space that is being used, and the amount of swap space that is free.