It uses MetaThesuarus to help you identify MeSH descriptors related to your query, and uses the descriptors to perform precision searches. It is well known that searching by descriptors will greatly improve the search precision. However, it is very difficult for people to know and use exact MeSH descriptors to search.
Searchers prefer to use their own words to express their questions.
The missing link thus is the translation of user's queries into queries based on MeSH descriptors. Visual MeSH tries to provide such link in many different ways. Using Visual MeSH, you can start with a simple query, the system will look up many MeSH descriptors related to your query, including Broader terms, Narrower terms, Related terms, and co-occurrence terms, etc. You can then interact with the terms and select terms that best describe your questions to conduct the search. It will then display a list of up to 100 MeSH descriptors used in the documents retrieved by the query.