(INSPEC is a propritary thesaurus from Web of Knowledge/Science)
Natural language searching and newer databases with responsive, custom search results are great for starting your research. They allow you to quickly see the lay of the land and identify general keywords to as you iterate and adapt your search strategy.
The best databases for the final stages of systematic prior art searching are transparent in how the search works. They allow you to be granular and precise with your keywords and phrases, and offer tools like proximity connectors to be as broad as you would like to be. They give you, the researcher, control over what you search. The traditional boolean search connectors are AND, OR, NOT, but, scientific research databases offer additional tools like proximity connectors, wildcards, and even regular expression.
Here are some links to the search syntax help guides of some the databases you may use in this course. To find this for other databases, use your preferred browser to search [Database name] Search Syntax. The help file from within a database will also typically have this information.