With this support, you are able to create a stopword list. This kind of list based on words which are ignored if you would search for them.
For example this could be terms, which appear often, but have no relevance for finding the correct content you are searching for, like »the«, »and« or »or«.
Or it could be special words, which could irritate the searcher with the search result. For example the term »Solar« instead of Solr.