A microapp is an app that is highly focused on performing just one task and doing it well. Learn what they are and how you can begin using them.
In software engineering terms, this is akin to the single responsibility principle which states that "a class should have one and only one reason to change." In other words, it only has one job and it, hopefully, does it well. Instead of having an app that has every task an employee can do, (e.g. report time off, submit expenses, choose benefits, search employee directory, upload shared resources, etc.) there are microapps that handle each of those tasks specifically.
As consumers, we've been using microapps for a while: the flight search box in Google, calendar alerts on desktop, WeChat, and so many more.