Bitcoin is an improved modern version of gold, or ‘digital gold’.
Mining either involves costs and an element of luck, scarcity gives both a value globally and both are vastly superior as an asset to fiat currencies that are inflated into oblivion.
However bitcoin is also provable, cannot be artificially produced, can be transferred anytime/ anywhere in minutes and is far harder to confiscate if governments feel like it.
BitGold is designed to be the size of a standard gold bar, but is obviously far rarer.