I have been familiar with the topic of bitcoin for a very long time. The truth is not engaged in mining. Now I would like to delve into the topic of cryptocurrency in general and in general. That is, what species exist, methods of extraction and exchange. And also, with which cryptocurrencies it is better to work with this, that is, it is more profitable and profitable. I think that there are experts on this interesting topic here. Looking forward to your advice and thanks in advance.