What does " " Mean in Formula

[NormanB]

I found a formula that I use in my check register type sheet. H is the balance column, F is the subtractions, and G is the additions. It will only show the balance if there is data in the row. It works great. I just do not understand why it works. Does anyone know what the "" means?

=IF(AND(ISBLANK(F6),ISBLANK(G6)),"",H5-F6+G6)

Thanks