
Com.po.si.tion: n. 1. The act of combining parts of elements to form a whole.
In the context of photography, composition simply refers to what you add in or take out of your picture combined with where you position every element in your frame to tell the story.
In other words, "Momma, you're in charge of deciding what story this picture will tell".Close up or far away, naked or dressed to the nines, every decision you make has a consequence in the message it sends through your photographs. Do you want to show the world that expression that every time you see it, melts your heart? Try filling the entire frame with your little one's face. Do you want to show how teeny tiny your toddler really is? Pull back and show her full body next to the oak tree in your back yard. Maybe it's the details that you want to capture since they change so fast! Zoom in on those tiny flaky newborn feet or long lush baby lashes.
Look through the viewfinder of your camera (aka- the eyehole). The viewfinder "frames" everything that will end up in the picture. You have important choices to make about what goes inside of this frame, and equally important choices about what will be left out! The possibilities are infinite, even with just one kid and a white background!
Luckily, there are some guides set forth by the photographers that have gone before us - guidelines that give us clues about what kinds of compositions naturally look better than others. Here are some basic ones:
Rule number 1 - Don't center your subject.
For reasons unknown to anyone but God and uber-snobby art people, pictures are just more interesting when your subject's eyes are slightly off center. Letting your main point of interest be either to the left or right or even above or below center makes for a more appealing composition. Ideally, if your subject is looking or leaning into your right, put their head on the left side of the frame. If they're looking or leaning to the left, you put their head in the right of the frame.
Notice how she is looking off to the right while she is sitting in the left of the frame

If you want to get really picky - it's helpful to imagine that your picture is divided into thirds vertically and h orizontally. Putting your points of interest at any of the intersections will help keep your composition balanced and interesting. It's called the rule of thirds - we didn't make it up, but we do find it incredibly helpful.
Rule Number 2 - Every picture should tell a story. If something isn't part of the story, leave it out! Take a picture, then look at it and tell the story out loud by going through each element in the picture and telling what its' role is. Are there things that don't have a part? Is something missing that was in your mind but isn't in the picture? Just like developing your eye to read light and watch for distractions, by doing this you will learn to see your story before you snap!
Notice the people in the background of this picture. Now if this were a picture of Chloë quietly doing a puzzle they would be distracting, but because this is the story of a birthday party, it makes sense to have them watching in the background.

Rule Number 3 - And the final rule! If it makes you smile, throw all other rules out. These pictures are for you to treasure and cherish, not for some panel of photo-snobs to give their stamp of approval. If it makes your heart sing - then you did your job!