If a digital camera says it is 1024 by 768 pixels, how many Megapixels is that? I'm only used to seeing them in terms of like 4.0 MP.

Multiply the two numbers, 1024x768=786,432. A megapixel is 1,000,000 pixels, so that camera is 0.78Mp. For good quality printed pictures you need around 3 to 4Mp, but if you're viewing them on a computer the figures you quote match the screen resolution of most monitors.