With image composition you enter a wide field of photography. After mastering the technical aspects of a camera, many people want to do the next stept. The taken pictures should look better, more beautiful, cause an "Aha"-moment for the observer and best should be displayed big framed as a piece of art in a galerie.
Ahead of it most people (expect some expections like natural geniuses) have to learn about image composition, image buildup and image effect. This is a broad field, which you can engage on diverse ways. Everybody who likes it scientific can read into Gestalt theory/ Gestalt psychology/ gestaltism, information theory and emotion theory.
Everybody who now says I don't want to follow rules, I want to break rules and take better photos that way, still has to bother learning the rules (or after Andreas Feininger "design proposals"). Because without knowledge of rules you cannot break them.
Let us take a look at some different ones:
Actual a simple story: humans want to understand what the picture is about with one look! This easily and fast recognizing (in prehistory important to know if somebody is friend or foe, to avoid being eaten when you don/'t run.) helps distinguishing between important and unimportant, between the figur (for example what you want to show as a photographer) and the background (what is also in the picture, simply because it is there). If you do not achieve to depict that when taking the photo you will get a hidden picture book, like where's wally, on which the observer can see a lot, but always asks what the photographer wanted to show.
If you have a "Where's Wally?" picture infront of you, then you cannot recognize what the picture is about. There is no separation between figure and ground or to explain it easier to understand: figur and (back-)ground.
This distinction between figure and ground is the most important finding of gestalt theory.
Or in other words:
There are some guidelines after gestalt theory, which you can use:
Ambiguous figure-ground-relations will mostly meet incomprehension. Maybe you are thinking of one of these typical ambiguous images (https://en.wikipedia.org/wiki/Ambiguous_image). Those who are a white vase or 2 black faces? Or the Necker-Cube – on which the human brain can only accept one form of presentation at the same time. Either the colored area in the front or in the back. But those are merely gimmicks, as in general photography doesn’t have such cut-out-of-the-environment objects.
So, back to our figur-ground-relation and why photographers love light-intense objectives. A big aperture opening (values of up-to 2,8 or depending on the recording situation a little bit more) makes it possible to let the background vanish into blurriness. And exactly because of that we get a perfect separation between figure and ground – mostly of a portraited person and the background, which isn’t recognizable anymore. That way you have the perfect example for figure-(back-)ground-relation. We could also follow Robert Capas saying: “If a picture isn’t good, go closer” in this aspect. As soon as you move closer you show the essential of the picture and a separation towards the background happens.
Maybe another excursion (and if you need a souvenir for kids) – beautiful where’s Waldo-style pictures are in this series „Wo ist Walter? “. you can also simply use the google image search.
Anyway … try taking some photos, where everybody immediately knows, what you want to show. And as a training take some real hidden object photos, where nobody will ever find out, what you wanted to show.