Cells may contain numbers, it may contain text values, it may contain error values and also it may contain nothing at all. As an excel user how do you know whether the cell has number, text, error or no value with it.
So here we have a category of information functions like ISBLANK, ISNA, ISNUMBER, ISERROR function. All these functions will return either TRUE or FALSE as their result. These functions are mainly used with other functions as logical tests.