A dollar today is worth more than a dollar later, because today's dollar can start earning interest right away — that gap is the time value of money. Present value puts a number on it: PV = FV ÷ (1 + r)ⁿ, where r is the rate per period and n is the number of periods between now and the future date.
Present value differs from net present value (NPV): PV discounts a future amount or payment stream back to today, while NPV goes a step further and subtracts an upfront cost, netting what you'd pay against what you'd receive to judge whether an investment is worth making.