Truncation allows you to get more out of your search term.
Often times the databases do not understand plurals.
For example:
A search of HARPSICHORD might give you 1,488 Results.
A search of HARPSICHORDS might give you 126 Results.
However a search of HARPSICHORD* will give 1,588 Results.
Truncation Symbols Vary:
Library Catalog and Most Databases is: * (asterisk)
Lexis Nexus is: ! (Exclamation Point)