Bitcoin is supposed to be a cryptocurrency,from the beginning.And is still cryptocurrency,the most accepted one.But with the time it´s also become an Asset.Fiat money is low risk asset but bitcoin is risky one
Bitcoin is not paper money because there is no physical, but the function is the same for payment and also for investment. Maybe what is meant is that investment is the same as assets, even though it is different because investment is something that is traded, while fixed assets only decrease or increase in value.