To quote practicallynetworked.com, syslog is:
... an industry standard protocol used for capturing log information for devices on a network, usually via UDP Port 514.
To put that another way, you can use it to monitor all manner of computers and network devices for information about what they're doing, or perhaps more importantly, what they're not doing!
Syslog comes pre-installed with all standard Linux distributions, and other Unix like operating systems. You can also get syslog servers for Windows, though Band Saw has not been developed with Windows users in mind.