Interactivity

Interactivity, by definition, is "allowing or relating to continuous two-way transfer of information between a user and the central point of a communication system, such as a computer or television." Interactivity on a website means that the viewer of the site has the choice to click on things, scroll over them, etc, and that in turn triggers a response. It can make an object move, bring you to a new site, bring up information, or a plethora of other things.