Is it backed by gold or a nation’s sovereignty?
Its value is achieved by its users ascribing “value” to it, as a medium of transaction, just like people used to ascribe value to beads, salt, feathers, precious metals, and whatnot throughout the ages.
For bitcoin, its value is in its deflationary characteristic, its network-centric characteristic, and its pseudoanonymous character.
Value has a subjective, human component. Understanding what “money” is is not taught in schools but to understand what a radical departure bitcoin is, you need to understand the history of money.