Ios 5 came along with a new set of keyboards: emoji
emoji are like smilies, but there are hundreds of them
you can enable them on your ios 5 or ios 6 device:
goto settings > general > keyboard > keyboards
click ‘add new keyboard’
scroll to emoji and select it.
now you will notice a new key on your keyboard next to the left shift ( a sort of globe symbol )
click that and you get the emoji!!