Definition - What does Interactivity mean?
Interactivity is the communication process that takes place between humans and computer software.
The most constant form of interactivity is typically found in games, which need a continuous form of interactivity with the gamer. Database applications and other financial, engineering and trading applications are also typically very interactive.
There are many software packages that run in the background without any need for input from humans or output to them -- that is, with no interactivity.
Techopedia explains Interactivity
A web browser is a common interactive program that most people deal with. During an online session, the web browser is the only interactive application that the user deals with. The code included in every Internet page defines a degree of interactivity with the user. For example, an online form needs input from a user and then it gives output in the form of labels that indicate the data to be entered in each text box or lists for the user to choose from.
Web based applications offer many forms of interactivity, including hypertext, which adds an embedded link to a text. Such interactivity provides higher readability and expands online applications to include video, audio and games.