A repeating decimal is one that essentially goes on forever. A terminating decimal is one that has an end, therefore a definite value.
The fraction 1/3 is a repeating decimal, because when you divide 1 by 3, you get .333333 (to infinity). To show that something is repeating, draw a bar (or line) above the number that is repeating, in this case, 3.
The fraction 1/4 is a terminating decimal. Like the one above, when you divide 1 by 4, you get a fraction. In this case, it is .25, which does not repeat.
The fractions are there just to show you how you could get to either, but your terminating decimal is .25, and your repeating decimal is .3 (but with a line over the 3 if possible).