Plug-in   A (usually small) piece of software that adds features to a larger piece of software. Common examples are plug-ins for the Netscape® browser and web server. Adobe PhotoShop® also uses plug-ins. POP   Post Office Protocol. Standard for exchanging Email between a users PC & their Internet Access Provider. PPP   Point to Point Protocol. Standard for using a modem & telephone line to connect to the Internet using TCP/IP.