The advanced search allow more granular research. Terms can be combined with AND, OR or NOT. 
The advanced search offer also the opportunity to limit the results to a specific resource type, a language or within a date range.

In this example the search is limited to books that contain "mountain railway" in the title and Switzerland as a subject.

With the aid of the second drop down menu, you can choose between “contains”, “contains (exact)”, “starts with (Title)”, to specify whether the search terms must be contained in the field, whether they must match the search terms exactly, or whether the item must begin with a specific term.

Here you can put a few key words, not necessarily in order

Here you are looking for those exact key words.

And here, you're looking for titles that start with the word "mountain". "Starts with" is available only for the criteria Title.