This online tool from the Google camp allows the average user to explore keyword relationships and trends on a deeper level. So a test with the keyword "Summer Time" displays relevant keywords based upon a common search frequency and search time period such as "fun pools", "sunblock" and "swim lesson"... hot stuff!
This is really next level insight - look at the same times of the year people are typing in "holidays to spain" the correlation of:
"magaluf", "cheap holidays to spain", "package holidays" and "self catering holidays"
appear giving a real nice overview of what people may also want concerning their holidays to spain.
Google Correlate produces visual graphs It plots the frequency between the correlated keyword and shows a strong fusion between the two. Not the best time for holidays to spain but regardless this shows that these keywords are practically symbotic. Now imagine how many relationships you can discover to get a better understanding of your customers and people in general.