Compound Path vs. Group/Ungroup

I agree. Also, all letters that have a hole in them (o,e,a,p etc.) are all compound paths, with the smaller path that is responsible for the ''hole'', having the node direction going in the opposite direction as the larger path. Groups do not care about node direction. So the use of a compound path is very different (has specific use cases) from a group. Great question form Winster.

This question makes sense to me and I'll try to answer it according to my understanding.
Both "Groups" and "Compound paths" can be considered "containers", meaning they contain different objects inside.
The main difference is that groups can contain any type of objects, for organizational purposes, without any interaction between these objects.
On the other hand, compound paths can only contain paths, and these paths interact with each other where there is an overlap/intersection to create holes. 
In the past, compound paths were interesting to group non-intersecting objects, as they would get treated as a single object for making a gradient that goes across all of them for example. Nowadays, the gradient tool got more advanced and it can be dragged uniformly across all the elements of a group too, so no need to use compound paths in this instance (but it's still not advanced enough to work with strokes). I think this described use case is the cause of confusion in this instance.

Maybe it is time to follow an online training, study the help file, read one of the many books about Illustrator.

Start learning the basics, your question doesn't make sense.

I don't want to sound harsh, but looking at your questions, that may be the best advice.