Full-text search is a battle between:
While matching only the exact words that the user has queried would be precise, it is not enough. We would miss out on many documents that the user would consider to be relevant. Instead, we need to spread the net wider, to also search for words that are not exactly the same as the original but are related (word stem, synonym ?)
keyword are the search term filled in the search form known also as search term
opensearch is a system that permits to make your internal search engine available publicly. Visitors can then searched directly from the browser.
There are three types of search intent:
the supported Google list, you can also add on into your analytics account
See What are models of text in NLP? (Natural Language, Text Modeling).
Lucene is the most known full text search library that powers:
Client Side Search. At its most basic functionality, a search component will simply provide an index file which is no more than a JSON file containing the content of all pages.