Lets take a look at Lenses:

If you don't have a DSLR - No worries! Many point and shoot cameras allow you to have control of your exposure triangle without changing lenses. In fact, lenses and exposure aren't necessarily related. So if you're working with a point and shoot, just tuck this information away for future use, should you decide to get a DSLR or mirror-less camera at some point.

If you do have a DSLR you'll want to know a few things about the lenses available. Lenses can be categorized under two basic headings: prime and zoom.

Prime Lenses

Prime lenses have a single focal length. For instance, the 50mm prime lens only photographs images at its 50mm focal length. Prime lenses are generally less expensive, yet offer higher image quality than a zoom lens. Prime lenses are usually “faster” than zoom lenses. This means the highest aperture on a prime lens is greater than the highest aperture on a zoom lens.

Zoom Lenses

Zoom lenses have a wide range of focal lengths. The popular 70-200mm zoom lens photographs images from 70mm to 200mm and anywhere between those two focal lengths. This offers the photographer the convenience of zooming in and out without changing lenses (or location). The more expensive zoom lenses have image quality comparable to a prime lens, and are usually "faster" than less expensive zoom lenses.

Focal Length

Wide Angle Lenses allow the photographer to capture more of the scene. For this reason, many landscape and architectural photographers prefer using wide angle lenses. A common focal length for a wide angle lens is around 15 to 35mm. Wide angle lenses used close to a subject can also create fun and playful distortion, as in the image above.

Medium Telephoto Lenses allow the photographer to capture their subject with a medium focal length. Many portrait and wedding photographers prefer using medium telephoto lenses for this reason. A common focal length for a medium telephoto lens is around 24 to 70mm.

Super Telephoto Lenses allow the camera to photograph images close up from a distance. Wildlife and sports photographers prefer using telephoto lenses for this reason. A common focal length for a super telephoto lens is around 70 to 200mm, but can go much higher. Many portrait photographers also like this range as they can give the subject some space but create a beautiful soft background with a wide aperture and distance.