In general the difference between series and shunt (or parallel) is that series is like a string of pearls, each one receives from a leading source and sends directly to a draining target (the current has to flow equally through all).
Parallel however is like a railroad track in that the source is one rail and the drain is the other rail with each of the ties pulling from one and pushing into the other regardless of what any of the other "ties" are doing (each has a completely separate current flow from the others).
In terms of regulation a series regulator would have to "block" some of the power going through it to the load in order to regulate it. A shunt or parallel regulator would have to "drop" or waste enough of the limited available power to restrict what would be left available to the load (or loads).
Hope this overview helps