From the post:
The following is written with Solr users in mind, but the principles apply to Lucene users as well.
I really dislike the so called “Boolean Operators” (“AND”, “OR”, and “NOT”) and generally discourage people from using them. It’s understandable that novice users may tend to think about the queries they want to run in those terms, but as you become more familiar with IR concepts in general, and what Solr specifically is capable of, I think it’s a good idea to try to “set aside childish things” and start thinking (and encouraging your users to think) in terms of the superior “Prefix Operators” (“+”, “-”).
Required reading if you want to understand how these the “Boolean Operators” work in Lucene/Solr and a superior alternative.