Swap is virtual memory that resides on a storage drive. This enables the server to use more memory than what is physically available, which can be helpful to cover memory overheads but can also degrade performance in some cases
For most servers, swap shouldn't cause a meaningful performance impact. However, servers which use a lot of memory directly from startup (heavily modded servers for example) can suffer more since the heap space is more prone to end using swap.
We recommend that you test with this setting on/off to see whether your server can benefit from it or whether the performance impact is too significant for your specific use case.
