[1] It measures the nominal future sum of money that a given sum of money is "worth" at a specified time in the future assuming a certain interest rate, or more generally, rate of return; it is the present value multiplied by the accumulation function.
The operation of evaluating a present value into the future value is called capitalization (how much will $100 today be worth in 5 years?).
The reverse operation which consists in evaluating the present value of a future amount of money is called a discounting (how much $100 that will be received in 5 years- at a lottery, for example -are worth today?).
Indeed, the Future Value in this case grows linearly (it's a linear function of the initial investment): it doesn't take into account the fact that the interest earned might be compounded itself and produce further interest (which corresponds to an exponential growth of the initial investment -see below-).
Alternatively the growth rate is expressed by the interest per unit time based on continuous compounding.
Compounding means that each successive application of the interest rate applies to all of the previously accumulated amount, so instead of getting 0.05 each 6 months, one must figure out the true annual interest rate, which in this case would be 1.1025 (one would divide the 10% by two to get 5%, then apply it twice: 1.052.)
The simplest way to understand the above formula is to cognitively split the right side of the equation into two parts, the payment amount, and the ratio of compounding over basic interest.