Can anyone explain SLR cameras to me?

I would love a SLR camera, but i just don't understand them.
What does Focal Length mean?
Lens Aperture? etcc..?
what!?

SLR = Single Lens Reflex.
This is a kind of camera that uses the same lens for you to compose the image and to take a picture. Most SLR cameras have a mirror between the lens and a sensor (or film) that is positioned at 45 degrees and reflects the light from the lens into viewfinder. When you release the shutter, this mirror flips up, and picture is taken, then mirror gets back into position. In some models there's a light splitting prism (or half mirror) that is permanently in place allowing the light to go both to viewfinder and to the sensor.

Focal length is a distance between the point where the light enters the lens and the media (film or digital sensor) The longer the focal length the greater is magnification.

Lens aperture is how wide the lens opening is, hence, how much light can a lens let in. The more light it lets in, the greater the aperture is said to be. It is measured as focal length divided by lens diameter. Because the aperture is measured as a fraction, the bigger number means narrower aperture. That is f/2.0 is a greater aperture than f/5.6. Usually lenses have special iris element that allows to close the aperture in order to control exposure. therefore a lens aperture is usually referred to it's widest possible opening. Also zoom lenses have variable maximum aperture because at longer end it's usually less than at shorter end, due to focal length increase.

etc.?
Shutter speed is how long the shutter is open for exposure, or in other words for how long the light is hitting the media (usually measured in fractions of a second, though there are applications that require full seconds or even minutes or hours of exposure).

Not only does an SLR display the picture through the same lense that it takes it, but it actually opens and closes its shutter. Point and shoot cameras just turn on there light sensors for a sec, while SLR's open and close the shutter, giving a cleaner picture.

SLR means that when you look through the "viewfinder" you are looking out through the lens that will actually "take the picture." Focal lengths, apertures, f-stops, shutter speeds, etc. are all things you need to learn if you want to experiment with what-all a full-function camera (SLR or not) can do. Otherwise, set the camera for full-automatic and you will probably get just-fine pictures. The other things ar avalable if you want to take photos in unusual conditions or to achieve special effects. If you are seriously interested, you can buy a book; check one out of the library; go to a decent bookstore and sit in ne of the chairs and study one of their books, or even do some Internet research. Best way, though, is to borrow someone's good camera and take a course in photography. OBTW: there are digital SLR cameras as well as regular analog SLRs