An int, which is short for 'integer' is a whole number. See the wikipedia article for general information.
In the GECK, any number which includes a fractional (or 'decimal point') part is rounded down (floored) when in an int context, such as when stored in an int variable.
int MyInt set MyInt to 5 / 2 ; will equal 2 set MyInt to 9.99999 ; will equal 9
In the GECK, unlike some programming languages, 'short' variables are identical to 'int'. Behind the scenes they are both technically stored as floats.