The Internet uses ``packet-switching'' technology. The term
``packets'' refers to the fact that the data stream from your computer
is broken up into packets of about 200 bytes (on average), which are
then sent out onto the network.
Each packet contains a ``header'' with
information necessary for routing the packet from origination to
destination. Thus each packet in a data stream is independent.
The main advantage of packet-switching is that it permits ``statistical multiplexing'' on the communications lines. That is, the packets from many different sources can share a line, allowing for very efficient use of the fixed capacity. With current technology, packets are generally accepted onto the network on a first-come, first-served basis. If the network becomes overloaded, packets are delayed or discarded (``dropped'').