For once (or twice, if I include the 'rule' that we respectively share with regard to the REQUIREMENT that one sprinkle grated parmesan cheese on their popcorn), I'm in agreement with User ID. (There may've been other times, too, but mentioning those might loose the red herrings of UHHville unnecessarily, and stink things up irrevocably....)

"LOOKS RIGHT". 'Plain and Simple' (for those who find themselves in the 'plain and simple' camp) or 'Order out of Chaos' (for those who subscribe to a more rationalized approach); choose either of these and if you haven't already done so, you'll begin to understand not only what composition is, more importantly you'll begin to understand the purposes and functions --and uses-- of composition writ large.

And the purposes, functions and uses of composition will never be understood until one first recognizes that the placement of elements in an image --and how those elements interact with/affect/mirror/oppose/define or even serve to negate one another should that be the composer's aim-- is precisely what makes a composition. Similarly, the purposes, functions and interactions of elements will never be understood until one first recognizes that things and objects are not merely objects and things; they're the stuff of stuff that can be ranked, have levels of importance or otherwise, of relevance and irrelevance in the ways that all things are ultimately connected, and that (to use an analogy, not knowing a better way to state it briefly) that music is not sound: music is sound AND silence that has been appropriately (i.e., RIGHTLY) placed. And as well, that color --its value, its tone-- is an element as much as a square or round or triangularly shaped 'object' is within a given space, and where and how it's placed matters, too. So to repeat, composition is how each of those elements 'relate' to one another, and that is what the basis of a composition actually is.