19 Sep 11 4:45 am
Global Monthly Searches is the average monthly searches over a period of 12 months for a keyword entered from anywhere in the world or the approximate number of searches of that keyword in the past month across the whole word.
In your example, does 1600 global monthly searches on exact means it is the number of searches per day? Exact means specifically that keyword and nothing else. So, the keyword is searched 1600 times per month using exact in match type.