So, Bitcoin is good for saving because it is a hard form of money compared to fiat currencies[, which are inflationary and lose value over time. You should save in Bitcoin, and when you want to buy something, you can spend your Bitcoin.
Bitcoin doesn't fit into this description, hard money is linked to currency that have backing in physical goods and services and can be dated historically to currencies tied to the value of precious metals like gold and silver and of which it's clear Bitcoin value isn't tied to physical asset.
It's value is however tied to it's decentralization and community driven activities like adoption, it's scarcity caused by limited supply, Blockchain security by action of miners among others.