PPP (the Point to Point Protocol) is a mechanism for creating and
running IP (the Internet Protocol) and other network protocols over
a serial link - be that a direct serial connection (using a
null-modem cable), over a telnet established link or a link made
using modems and telephone lines (and of course using digital lines
such as ISDN).
Using PPP, you can connect your Linux PC to a PPP server and access
the resources of the network to which the server is connected
(almost) as if you were directly connected to that network.
You can also set up your Linux PC as a PPP server, so that other
computers can dial into your computer and access the resources on
your local PC and/or network.
As PPP is a peer-to-peer system, you can also use PPP on two Linux
PCs to link together two networks (or a local network to the
Internet), creating a Wide Area Network (WAN).
One major difference between PPP and an Ethernet connection is of
course speed - a standard Ethernet connection operates at 10 Mbs
(Mega - million bits per second) maximum theoretical throughput,
whereas an analogue modem operates at speeds up to 56 kbps (kilo -
thousand bits per second).
Also, depending on the type of PPP connection, there may be some
limitations in usage of some applications and services.
