There is a wealth of information out there if you google it.
Basically this occurs when a boiler is oversized for the heating demand. If you have multiple heating zones and only 1 or some of them are calling for heat the boiler fires and gets to temp quickly. This happens over and over causing ineffiecient firings.
The longer the boiler runs the more efficient it is.
There are outdoor resets, heat managers to help with these conditions. Basically advances computers controllers to throw some smart at your boiler.
Or if you are replacing your system you can fix the problem with a properly sized boiler and or a modulating one that can fire only at the BTU required to satisfy the heat demand at that point in time.