FTP is the most common service used that allows you to move files into your Web space for others to see. In its simplest form, it is as basic as copying/pasting files from one folder to another, something you probably do on a daily basis on your computer already.
There are a few pieces of software available that can facilitate FTP transfers for you, such as WSFTP, FileZilla, CuteFTP and Fetch. You can use your browser window as well, if you'd prefer not to install additional software onto your computer.