The focal length of a lens determines its angle of view (how near or far something appears, even how distorted the image appears). This Cambridge in Colour site has more information than you’d probably ever want on Understanding Camera Lenses. Let’s look at some photos taken with different lenses.
According to Wikipedia, wider lenses tend to magnify distance between objects while allowing greater depth of field. You may have heard of a “fisheye” lens (common in skateboard photography and video). To read more about wide angle lenses, check out the Cambridge in Colour site. Here’s a link to some spectacular photos taken with wide angle lenses. Here are some examples of my own:
A telephoto lens is a long-focus lens in which the physical length of the lens is shorter than the focal length. This extends the light path. Below is an example comparing zoom and non-zoom:
Check out this image comparing wide-angle and telephoto lenses from Cambridge in Colour.
Macro photography captures images close up (sometimes more than we can see with our eyes). These lenses produce an image on the focal plane (i.e., film or a digital sensor) that is the same size or larger than the subject being imaged. These lenses are used for “close up” photography and bring the focal plane “forward” for very close photography. The depth-of-field is very narrow. Below are a few examples, but you should also consider checking out Natialia Maks close-ups of objects in a garage.: