Good Keywords is for finding the common words people usually search for. 

For example if you type 'computer' the Overture/GoTo search suggestion tool will tell you that during the last month the word 'computer' was searched 459549 (these numbers are not exact and are used as examples only) times at Overture.Com. Similarly 'computer game' was searched 302207 times. Also, given one word it will tell you all relevant combinations of that word (again this is based on actual searches done by people). 

If the word you typed in not a common search term you will not get any results. It simply means that very few people actually searched for that word during the last month. 

The Lycos and Teoma component of Good Keywords will tell you the other combinations of keywords similar to the one you typed in (related searches). If these search engines have no suggestion it doesn't mean that there are actually no search results. 

The software is useful for researching how people search the web and then optimizing your own web pages so that more people find your web site.