What com.apple.diskspaced service does? What is the purpose of com.apple.diskspaced? What this service does exactly?

$ launchctl list com.apple.diskspaced
{
    "EnableTransactions" = true;
    "LimitLoadToSessionType" = "Aqua";
    "MachServices" = {
        "com.apple.diskspaced" = mach-port-object;
    };
    "Label" = "com.apple.diskspaced";
    "TimeOut" = 30;
    "OnDemand" = true;
    "LastExitStatus" = 9;
    "PID" = 96227;
    "Program" = "/System/Library/PrivateFrameworks/StorageManagement.framework/Resources/diskspaced";
};
I think this service check your available  disk space. 
If you have less than N% (~5%) of your HDD it will show a notification.

Until macOS Sierra this notification could be silenced by selecting (Don't show this again) but on macOS Sierra you no longer have this option.

I have 2% left on my HDD and I had to manually remove (Activity Monitor -> Quit) this daemon so I don't get this annoying notification.

I have searched for a decent way to stop this notification but I think there is only this solution.

Hope this help.