Looking at your camera, let's identify some of the important parts that we'll be referring to. The lens is the shiny thing you point towards your subject. Inside of the lens is the aperture, a thingy that works like the iris around the pupil of your eye. What that's for we'll get to soon.

If you have a DSLR you can take the lens off. There's usually a lens release button very close to where the lens meets the camera body. You'll push on the lens release and twist the lens so it'll come off. 
- Don't drop it.

A word of caution: when you take the lens off of your camera you open your camera up to the outside world. And that's when dust and little fuzzies can get in there. So, if you take the lens off, don't keep it off longer than needed.

When you do take the lens off, you should see the mirror right inside the camera body. Or, if it's a mirrorless camera, you won't see the mirror, but rather the chip that will record your photos.

You should never touch anything inside of your camera. Whatever is going on that may lead you to want to touch things in there, you'll most likely make things worse, or break them altogether. So, don't!

Here's the important part:
On most cameras and lenses there are small marks in the form of a red dot, a white dot, or a white square. These are there to help you to find the right position to put your lens on your camera by lining them up to each other. When you put your lens back onto your camera you'll have to twist it until it locks. You'll know that it locked when you hear a click. If you do not hear that click your lens is not completely secure. So, the click is fairly important.

Your camera has a shutter that controls the time your camera is open to let light in. That shutter is usually behind the aforementioned mirror. If you have a mirrorless camera, the shutter can be electronic, so you won't be able to see it.

In the right picture you can see a lens hood. Some lenses come with one. It is used to help you avoid lens flare if you're photographing directly into the light. I found though that it is an excellent option to protect your lens. If you have one, it should be on your lens any day that ends with y.

That mirror I keep talking about is used to take the projected scene that comes in through the lens and reflect it up to the viewfinder. The viewfinder being that bump on top of most cameras, where you look into it from the back. 

Sometimes you can also use the back display on your camera as a viewfinder, but that only works when you're not in the blazing sun. I find that the look-through viewfinder seems to work the best for me, as I can see what's happening under almost all conditions.   

For you to practice:
Take the lens off and put it back on, listening for the click.