Lenses with a short focal length (e.g. 18 – 35mm) with a wide field of view, are known as wide angle lenses, ones in the region of 50mm are known as “Normal”, as they’re close to our own sight, and ones beyond 50mm – from about 70mm upwards, are known as “Telephoto”. The lower end of this range – 70mm to about 105 is usually known as a short telephoto, and beyond about 200mm known as a long, but this is more of a turn of phrase, so you’re better off being specific with numbers if you’re just starting out. Don’t forget of course, that these are the numbers for “full frame” sensors – if your sensor is larger or smaller, then wide, normal and long will all be different numbers, but will still follow the same progression of wide being a small number, and long being a larger number.
Outside of the basic rules of exposure, and some of the underlying physics of things like sensor size, there aren’t really any rules in photography, but there are conventions. As with so many things in life, it’s worth knowing these conventions so that you can play along when it suits you and break them when you feel the need. Conventionally, wide angle lenses are used for landscape photography, normal and short telephotos (70-100mm or so) are used for portraiture, and longer telephotos (200mm +) are used for sports, and wildlife photography – anything where your subject can be a long way away. The convention exists because a wide lens allows you to get lots of landscape in, a normal or short telephoto has a flattering perspective for people – and doesn’t distort like a wide angle will, and a long telephoto will bring the action closer if it’s the other side of the field.
However, there’s no reason not to use a wide angle to shoot sports action, or a telephoto to shoot landscape – once you’ve got the feel for what different lenses can do, you should simply see them as tools for the job, rather than a set of rules.
There are several other lenses besides these three broad types though, and they can be all sorts of fun. Fish eye lenses, as the name implies, give you a hugely wide angle view, distorted like that of a fish. If you’ve ever shot with a Go-pro, you’ll be familiar with this view.
Tilt+ shift lenses allow you to move the lens in relation to the camera, mimicking the movements you can get with large format cameras – they’re very expensive, and very clever, but unless you plan on doing a lot of architectural photography, I’d suggest you only hire them when you need them.
A very common “speciality” lens, is a macro lens, which allows you to photograph things in close-up. Many zooms have a “macro” function, but all this really means is they can focus quite close – they won’t actually go to 1:1 size like a true macro. You can go even closer by adding extension tubes or bellows, which will let you get beyond lifesize