Listofsymbols provides commands to automatically create a list of symbols (also called notation or nomenclature), and to handle symbols logically, i.e., define a macro that is expanded to the desired output and use the macro in the text rather than hard-coding the output into the text. This helps to ensure consistency throughout the text, especially if there is a chance that symbols will be changed at some stage. The package is more or less a combination of what the packages nomencl and formula do. The concept of creating the list of symbols, though, is different from the way nomencl.sty does it.