Pixels and Megapixels

What's a megapixel you ask? First, let's just consider a pixel or picture element. A pixel is one of the square "dots" that make up your picture. When you take a picture your camera transfers the contents of a rectangular sensor to the memory card in the camera.
Every rectangle has a height and width. Suppose the camera sensor is 3000 units wide and 2000 units high (where each unit is a pixel). Simple arithmetic gives an area of length x width = 3000 x 2000 = 6,000,000.
That sensor records 6 million pixels. To keep the numbers under control, a megapixel is 1 million pixels. So our 6 million pixel sensor is a 6 megapixel or 6 mp sensor. And that makes the camera a 6 mp camera.