Photography is the science, art, application and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. Photography is employed in many fields of science, manufacturing (e.g., photolithography), and business, as well as its more direct uses for art, film and video production, recreational purposes, hobby, and mass communication. - Wiki

In photographyshutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a photograph.[1] The amount of light that reaches the film or image sensor is proportional to the exposure time. ⁄500 of a second will let half as much light in as ⁄250 - Wiki

In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane.[2] If an aperture is narrow, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. A wide aperture admits uncollimated rays, resulting in a sharp focus only for rays coming from a certain distance. This means that a wide aperture results in an image that is sharp for things at the correct distance. The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time). In the human eye, the pupil is the aperture. - Wiki

How much light is needed is determined by the sensitivity of the medium used. That was as true for glass plates as it is for film and now digital sensors. Over the years that sensitivity has been expressed in various ways, most recently as ASA and now ISO.

The "normal" range of ISO is about 200 to 1600. With today's digital cameras you can sometimes go as low as 50 or as high as 204,800. The number chosen has two important qualities associated with it. First, it sets the amount of light needed for a good exposure. The lower the number, the more light required. The more light that's required, the more likely a slow shutter speed will have to be used. -

A camera body is the primary part of the digital camera, which contains the controls, the LCD, the internal image sensor, and the associated circuitry, containing all of the components needed to record the photograph. It's also the part of the camera that you'll hold when using the camera - Lifewire

A camera lens is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically. - Wiki

Camera Strap - attached on both sides of the top of the camera, usually, draped around the neck. I prefer the neck straps, traditional straps, as opposed to the other varieties of hand, waist, or bottom-mounted straps. Keeps my hands free, I know how to move with a camera around my neck, which I can switch to my hip quickly. Ultimately, don't let your camera fall. That's an expensive necklace. Some folks even prefer using two cameras at once, for different perspectives without having to change lenses. I prefer one, because changing lenses is easier to me than juggling two cameras on my body. Two cameras increases chances of damaging equipment or hurting yourself, or both. I don't always dangle the heavy piece of equipment around my neck, but I do let it sit there when my hands are busy adjusting the hair on a client's face or holding the bouquet while a bridesmaid fluffs the dress. I carry my camera in my hand the majority of the time, because it would cause neck problems if I didn't! That strap is an extra helper. It's there as an insurance policy if I drop the camera and it's there as a convenience factor when I need to move quickly. If I had a hand grip, I would have to set the camera down each time I needed both of my hands. If I had a swivel attachment at the bottom paired with a strap, I'd have to let my camera dangle upside down, having to take extra care not to let it flop or jerk around and hit something. If I chose not to have a strap at all, I would again have to set the camera down each time I needed my hands. If I got a body strap and connected that to myself, I wouldn't be able to drop to the ground comfortably and quickly for a special candid shot or perspective. I prefer the camera strap that comes with the camera, because it is simple to wear and simple to remove or adjust to wearing it on the hip on the side or entirely on the neck.