I asked because I was confused. I just thought that it is trading bitcoin with bitcoin.
You basically have it. To complicate thing a bit bitcoin is a global currency. So you might be buying in Yen and selling in Euro, but still a trade on valuation. Of course the price could srop 30% and you may have to wait years to see a profit.
Bitcoin is not a stock or a bond and was not invented to trade like that. Many people have lost all their money trying to trade. Bitcoin is a currency and you can do very well without selling. I have never sold a bitcoin and yet I realize a fortune in saving just spending it. If all you do is trade it you have not yet seen the true power of bitcoin.
Thank you for explaining. I guess I was right with the buying / selling part, but with the addition of different world currencies.
Locking this thread, since I got the answer. Thank you @RodeoX