A Dollar Today > A Dollar Tomorrow
More is more & less is less, right? Depends. With money, it depends on:
When
How sure
If I give you a dollar today, you can spend it on something you want or you can invest it in a way that gives you more money later. If I promise you a dollar tomorrow, it's worth less than the dollar I give you today.
You can't spend it, so it's worth less.
You can't invest it, so when you get it it will be worth less than the dollar you got today.
There's some chance that I won't actually give it to you. Well, not me. I'm entirely trustworthy. But someone else, yeah, you have to be prepared that they won't give the dollar, making that "dollar tomorrow" worth less.
How much less? Complicated question.