What "global monthly searches" on Google key words means?

for example when I write a word on the keyword tool and it shows 1,500 searches under "global monthly searches" what is that means. Is this means the word is searched a 1,500 a month or 1,500 a year or how often.





In the help google says this is: The approximate 12-month average of user queries for the keyword on Google search. This data is specific to your Keyword Match Type selection.





What exactly " approximate 12-month average of user queries for the keyword " means.





Is the search for 12 months ( 1 year) or one month.





Thanks|||Global monthly search means the particular word is searched for a month by the whole world. it just show 1 month volume.