Investing bitcoins are my favourite hobby. I always invest bitcoin on forex trading, altcoins trading.
it helps me get more earning than anything else. Moreover , investing bitcoins is buying and holding bitcoins when it's down.
I do not know trading is included in the investment or not? I think the investment is not necessary to work to grow your money, you just need to put bitcoin in it and it will grow, but with trading you have to work to find the right time to buy and sell and look for altcoin potential?
In general, investing is when you put money and you are expecting a return in the form of profit, that's why we risk our money by investing to earn. What you are saying about holding your bitcoins is also a form of investment, the volume may not grow but the value surely will, with that you can earn profit by the time you exchange it to fiat.