Only a few years ago, web search was simple. Users typed a few words and waded through pages of results.
Today, those same users may instead snap a picture on a phone and drop it into a search box or use an intelligent assistant to ask a question without physically touching a device at all. They may also type a question and expect an actual reply, not a list of pages with likely answers.
Search is a very complex topic. Try thinking how would you build a competitor of Google Search and you will immediately start realizing the huge mountain that you need to climb. As the article mentions, the problem now is that the users are not satisfied anymore by having a list of related websites, they just want to have the answer.
This creates an entirely new set of challenges for the search engines, and this is what this article is talking about. In this article, Microsoft shows how they are trying to solve this problem and they open sourced a library that they developed for this.