[IvanN]

Large-scale integration (LSI) is the process of integrating or embedding thousands of transistors on a single silicon semiconductor microchip. LSI technology was conceived in the mid-1970s when computer processor microchips were under development.
The contents of a webpage are crawled by a search engine and the most common words and phrases are collated and identified as the keywords for the page. LSI looks for synonyms related to the title of your page.
Example, if the title of your page was “Classic Cars”, the search engine would expect to find words relating to that subject in the content of the page as well, i.e. “collectors”, “automobile”, “Bentley”, “Austin” and “car auctions”.