The INT function
in Excel is similar to the ROUNDDOWN function
in that it is used to reduce the number of decimal places of data. How it differs is that it always removes all decimal places leaving only the whole number.
Unlike formatting options that allow you change the number of decimal places displayed, Excel's rounding functions actual alters the data in your worksheet and can, therefore, affect calculations.
To find out all the details, read this short tutorial on the Excel INT Function.
More Rounding Number Functions