A system update will either update the current operating system or various files in your PC to use the PC better and by better I mean with more compatibility for apps, better functionality for devices, system stability, system protection, virus protection, etc.
A system updated is always recommended to be done by the user. In most of the cases, when you click Details on the Update page in the software, a changelog should appear as well. You can read there about the changes in the new system update.
In my opinion, you should update the system/OS.