A Int Is from 2,147,483,647 to -2,147,483,647 and is a signed 32 bit integer.
An integer is number without a decimal, also known as a whole number. Trying to put a number in like 20.34 will just delete the decimal part, making it store 20. It will always remove the decimal part and return the whole number part when storing a number, no matter how big or small the decimal is.
Links to more in depth explanation beyond the scope of this wiki: