"Stars" are commonly referred to as "Poles" as well.  Yes, they are vertices that have more than 4 edges connected to them.  These are NOT always a bad thing, and unavoidable in some cases.  Poles can be used also to direct edge flow, and are usually created from extruding faces while modeling.  You need to be mindful to keep them away from areas where the mesh will deform, however, as they will cause artifacting, even if all the polys around them are all quads.

Let's say, while modelling, you extrude an arm from the body of a character.  It's a common thing to do.  The extrusion process itself may create poles at the corners of polygon(s) that you extruded from.  Everything is still quads overall, but now you may have 4 areas on the mesh where edge flow will need manual adjustment, because it's an area that will certainly deform.  So that's a tricky area on any character that can cause problems if you don't know what you're doing there, and don't understand edge flow.

It's also helpful if you're working with a modelling application that has robust edge control.  Pinching, sliding, and other features are helpful, but there's a lot more to it as well, like edge spinning and retriangulation tools when working with quads.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.