•Browser extensions allow a Web browser to perform tasks it was not originally designed to perform. •Plug-in:  integrated browser software that the browser uses to display or play a specific file that you request. •Helper applications: programs installed on the user’s computer that the browser starts and uses to “help” display or play a file. •Add-ons:  include tools that enhance your browsing experience, such as toolbars or programs that block pop-up ads from opening.