Well, using networking like the first tutorial, you're obviously only able to send one little bit of data to another computer, and it has to be an array of characters. Packets, are streams of data, (like using std::cout) and they hold lots of different types of data, like integers, strings, the basic types, and then you can make your on structures that you can assign directly to a packet. Packets are basically ways of storing lots of different kinds of information, and sending it over the network.