What she means is that a dollar does not buy the same amount of things as it used to. Take a .05 cent candy as an example, in year one the candy costs 5 cents which means you can buy 20 candies. In year 2 the price is .08 cents and you can buy 1/.08 = 12.5 or simply 12 candies. Assuming the candy hasn't increased in quality, this is known as inflation.