All about digital cameras?

I'm probably getting a nikon d3000.So can you tell me all about shutter speed, iso, and whatever this f2.8 stuff is about? Also anything else that might be helpful?

This is your job to learn camera and basics of photography. You should know the basics Before you buy a DSLR.

You are asking for someone to type you any entire photography class… Not going to happen. Buy and read a book called "Understanding Exposure." It is cheap, short, and easy to read. There's no better book for a beginner with a DSLR.

First get the D3100.It's newer, and more versatile. (I've got one, and I had the D3000)

Next, the ISO stands for International Standard of Operation in regards to light sensitivity. Lower ISO ranges 100-200 are less sensitive; good for a day at the beach, while higher values like 1600-3200 are good for school auditoriums. Just know that high ISO values are trying to "see" what the light may not allow for, and some pictures may have a lot of "noise" or pixelation in the darker areas where the camera is trying to render what is there.

Shutter speeds are (in digitals) how much time the sensor has to process the light information. Smaller fractions from 1/500th of a second to 1/4000th sec. Are better used for action shots. 1/800 to 1/1000 is all that's needed to stop a humming bird's wings.slower shutter speeds are for harnessing ambient light for producing richly colored pictures and low light situations, where you need to use all the light you have available; 1/10 sec.down to 30"sec.

as for "f2.8" The f stop is the focal length. It controls two things, light entering the lens and sensor, and your "depth of field". Depth of field is how wide the area around your subject (front to back) is in focus.smaller f stops like 3.5 (2.8 is only on high performance, expensive lenses) allows more light for a faster shutter and lower ISO, but only have a small field of focus. At 50mm zoom, using an f stop of 8 or 9 would show the entire face of someone you if you were to be taking a bust style portrait. Just know that a greater f stop will allow less light to reach the sensor because the f stop is the lens' aperture. It contracts with higher values and dilates with lower ones.

All of these, and more, work in tandem to make your camera able to produce anything you can think of. Practice is key. Hope this helps!
Regards,
Deven