What on earth does a "grid" actually do?

I was asked recently what the purpose of a grid is on a flash, and while I can explain it easily enough a picture speaks a thousand words so here are about four thousand words worth in pictures! (...and a little text)

First up a flash firing directly at a wall (with a framed drawing hanging on the wall) without any attachments whatsoever:

As expected there is a large spread of light across the entire wall in front of the flash. The flash is set to 35mm.

Next up the exact same shot but with a grid attached to the front of the flash:

Outdoor Portraits on a Grey Autumn Day in Sweden

Autumn in Sweden is a dull overcast cold and damp affair as the season changes from glorious Swedish summer to beautiful Swedish winter and aside from a few lovely sunny days when the colours come alive it generally isn't great weather for photography... or is it? I went out to take some portraits yesterday and I figured that the dim light combined with autumn enhanced trees would make for a nice environmental setting to utilise as a backdrop.

In order to make the subjects stand out from the dreary autumn background I took along one of my trusty speedlights, a long pole and a shoot through umbrella. This makes for a very simple outdoor lighting setup but please note that you will need an assistant to help you with that long pole or you could drive yourself insane trying to keep control of the light and camera at the same time. The pull back shot looks like this: