I think they just picked the sentences that contained the keywords, and concatenated them together (if necessary because the sentences are in two different loca

I think they just picked the sentences that contained the keywords, and concatenated them together (if necessary because the sentences are in two different locations). The sentences themselves can be found using basic word searches once the content is parsed/indexed (obviously, the Google indexing/searching is more complicated than that). Both of my company's database engine products offer this type of functionality, as do many database engines/servers out there. It's typically referred to as full-text indexing or full-text searching: https://www.postgresql.org/docs/9.5/static/textsearch.html https://www.postgresql.org/docs/9.5/static/textsearch.html and there are lots of ways to control how/why certain words are indexed/search (stop words, synonyms, stemming, etc.). With the right amount of customization, you can get pretty close to ideal search results.