One “kind” of being, three actual beings of that “kind.”  That’s it.

The concept of the Trinity (God = one in essence and three in persons) is not hard to understand.  There is no mystery to it.  People just get tripped up with the semantics.  

If I have human triplets (who would then have a human nature [nature x]) that each grow up to have the same moral character (character y), they would all be one in essence or nature (nature x + character y = essence).  Three persons, one essence.  

What’s so hard about that?

Here … I’ll make it even easier.  The following letters have the same essence/nature as letters of written communication with the same size even, same shape, same everything, except there’s THREE of them:

X X X 

What’s so hard about that?

So … God, as defined by the Nicene Creed teaches that there are three beings who are divine, and therefore each have all that is appropriate to that divine nature.  Three persons … one divine nature.  One “kind” of being, three actual beings of that “kind.”  Simple.  Easy.  Fun.  Yippee.  Yay.