You spend time to work and create value.
You want to exchange your value with a tool many would accept.
You create this tool and call it money.
Money when used to store its value during time should be hard, not infinite or controlled by some entity or central power, like FIAT is (dollar, euro, etc).
Bitcoin is many things. 
Is a protocol, is digital property, is money, is saving.
It is a tool which you can use to save your time not being worried that a central entity could change its rule, can't prevent you to be part of it, can't censor your transactions, can't take your time.