The term "title" is a bit of over-simplification. The actual match is on the lines in the index files, and those lines contain more than just the titles. Also, the string that you type is treaded as a perl pattern, and capitalization is ignored. But the obvious case works: If you type a tune title, or a portion of a title, you will get a list of the tunes that contain that string.
The various options are for changing this behavior. Note that the option names are links to documents that describe what they do. And some of them (such as Sel and Threshold) are rather experimental.