Help please, what does the following formula mean?

=COUNTIF('anotherworksheet'!B:B,"'Area'")

I understand the countif function and the reference to another worksheet. I
am not sure how the "!B:B,"'Area'")" reference works. The result of the
formula appears to be count of the number of rows with values in a column
named "Area" in cell B1. I am just not sure now the and the "Area" are used.

Thanks in advance,