A "camera" is, in its simplest form, like a box with a hole in front of it. There is a special piece of glass in front of the hole called a lens. To take a photograph of something, the lens makes a small picture of the object inside the camera. The lens does this by focusing light. A lens in a camera works like a lens in glasses (spectacles) or a magnifying glass. One type of camera called the Pinhole camera has no lens but uses a very small hole to focus light.
To make a photograph with a camera the shutter release button is pressed. Pressing the button opens the shutter. The shutter is like a door. It covers the hole in the camera box. The shutter is behind the lens. When the shutter is closed no light can enter the camera box. When the shutter is open light can enter the camera. When the button is pressed the shutter opens and then closes. This happens very fast. The amount of time the shutter stays open for is called the shutter speed. The shutter speed can change between 1/1000th of a second (0.001 s) to a few seconds. Normally the time taken for the shutter to open and close is far less than 1 second.
Some cameras have an aperture ring. It controls how much light enters the camera box.
The photograph in a camera may be made on film or, if it is a digital camera, using an electronic sensor.
A simple video explaining the basics of photography