I found Something like this ->
Average monthly searches ("Avg. monthly searches"): The average number of times people have searched for a keyword and its close variants based on the month range as well as the location and Search Network settings you selected. You can use this information to see how popular your keywords are during different times of the year. By default, the number of searches for the term (regardless of language) is averaged over a 12-month period.
Volume - It is the estimate search volume of a particular keyword that people search on Google on a monthly basis. It tells you the maximum potential of a keyword that you are willing to rank in Google’s top positions.