As a web developer, one of my code tasks is to deploy a website to a live environment. This boils down to copying lots of files in lots folders from my development environment (a Windows 7 computer) to a live environment (could be Linux or Windows). To give you an idea of what "lots" can be, a typical Magento installation without any customisations, themes or 3rd party components weighs in at around 10,000 file across 3,500 folders.

I also like to propagate changes from a live environment back to my dev environment (or at the very least be aware of such changes so they don't sneak up on me in a dark alley).