eval function

[ananth21]

what is and how to use eval function. here is what i read from a python text book, "a built-in function that treats a string as a piece of executable program code"
i dont really know what an executable code is.
kindly explain eval function with a little example so that i can understand better.
thank you

[bvdet]

Following are 2 simple examples:

>>> eval("2*6")
12
>>> x = 100
>>> eval('x')
100
>>>