We simply mean a promise that one party makes to another part to do something in the future.
Any token that represents a redeemable (exchangeable) commitment,
I owe you...
I will pay you later for that now.
I will give you this for that.
How much does that cost?
If you do this I will do that.
If that happens I will give you this.
I will return this (or its's equivalent value) within this time or on this date.
This is worth two of those.
There are not enough of those to go around.
There are too many of those for them to be worth much.
I bet that this will become more valuable over time with me doing anything.
I can obtain rent for this.
I will pay rent for that.
This is worth less over time.
This gets destroyed in use.
This pretty much stays the same with use.
I can easily keep this away from others or others away from it.
This costs little or nothing unless we make it scarce.