In 1995, a company known as Netscape Communications Corporation, which had developed a web browser, called Netscape Navigator, wanted to incorporate interactivity to the browser.
In web development jargon, interactivity refers to the ability of a website, running in a browser, to provide immediate feedback to its users.
To illustrate, consider a website that has space for its user to enter some predetermined value. The website is said to be interactive if it is able to detect and inform the user, in real-time, about whether or not the value they entered is valid.
As you can see, interactivity is a feature that can make websites engaging. Yet, as at 1995, it did not exist in any web browser. Netscape thus decided to make their web browser the first to incorporate it.