Please understand, this tutorial is for absolute beginners and its pretty much straightforward and presented with some really basic jquery syntax examples.
Linking to jQuery's source code remotely
This is one technique which developers and php programmers are using today. In this way, programmer don't have to download and save jquery file on their machine. however, you must have really good internet connection for remote method to work. If jquery file from remote url is not downloaded properly, your application wouldn't work. It also means, if remote website is down, then you code will not work as well.