A plug-in extends the capabilities of a web browser, such as Netscape Navigator or Microsoft Internet Explorer, allowing the browser to run multimedia files. The term "plug-in" is used in two ways on the Internet. The technical definition of a plug-in is a small add-on piece of software that conforms to Netscape Navigator standard. Other browsers however, including Internet Explorer, support many Netscape plug-ins. But Explorer actually uses a different software standard, called an ActiveX control, instead of plug-ins.