Software that is responsive gives the user an output or a confirmation of input quickly. It does not block the user from preforming actions without a very good reason.

Software that is responsive is very important for user engagement because sluggishness often results in frustration and abandonment.

While making responsive software is the subject of many books and tools, two additional things should be kept in mind. First, that performance must be considered a feature from the start, not an afterthought or a bug to fix. Secondly, for interactions that are slow that cannot be further optimized there are ways to give the illusion of speed in order to improve reponsiveness to the user. For instance loading critical parts first and using skeleton screens.

Responsive software goes hand in hand with giving instant gratification to the user.

Examples of software being responsive

Google uses skeleton screens to show the structure of the content and create the illusion of speed even when processing might take time.