When you first visit the Advanced Search page, you are presented with several search fields. In each field, you can type the keywords you want to search for. Search operators are allowed.
Each field is accompanied by a drop-down that lets you specify the type of data (title, author, etc.) you are searching for. You can mix and match search types however you like.
The "Match" setting lets you specify how multiple search fields should be handled.
The "Add Search Field" button may be used to add additional search fields to the form. You may use as many search fields as you wish.
For certain complex searches, a single set of search fields may not be enough. For example, suppose you want to find books about the history of China or India. If you did an ALL Terms search for China, India, and History, you would only get books about China AND India. If you did an ANY Terms search, you would get books about history that had nothing to do with China or India.
Search Groups provide a way to build searches from multiple groups of search fields. Every time you click the "Add Search Group" button, a new group of fields is added. Once you have multiple search groups, you can remove unwanted groups with the "Remove Search Group" button, and you can specify whether you want to match on ANY or ALL search groups.
In the history of China or India example described above, you could solve the problem using search groups like this: