Cryptocurrencies are ponzi scheme! 
Yeah, I thought that too. That explains the ups and massive downs.
There's a ton of crap to sort through with all the different cryptocurrencies. The only one that ever interested me is XRP (Ripple), which is a transaction platform with actual utility for foreign exchange, interbank, etc - it was sort of imagined to be a complement to SWIFT or what retail customers might think of as the ACH network. I can't bring myself to try to differentiate it from the rest, as I'd need to rest my wrists for an hour (and maybe want to slash them) after I got done explaining, but it's had self-settling contracts ('smart contracts') from the beginning and is currently in use or in testing by a number of international banking consortiums and central banks. Bank of England just did a trial run with it recently, etc. I own some of the platform currency (XRP) from back when I played around with it, like five years ago - happenstance, actually, I'd totally forgotten that I'd even bought some to do some testing. It was started by Prosper's founding CEO and came to my attention because of that, at the time. Now, it's apparently getting popular with individuals - in addition to all the government/government-sized institutions. Who knew? Maybe I'll make a buck or two. Individuals can use it, and buy it, but it's almost harder to figure out than all the rest of them and doesn't have many small scale applications in its user ecosystem - mostly just the big institutional kids --- or so I thought... One of the interesting things about it is that it's got a very granular set of "graphs"; "quantification of trust" (per aspect/entity/node) or built-in risk-management (capable of 'contagion-control', probably why the central bankers like it so much) mechanism/system being one of those sets of interlaced/interpolated graphs, almost a realtime network trust graph, with each node having currency gnostic/agnostic, per entity, credit / timing / window controls........ anyway... if anyone cares, go play with it a bit - that's the best bet to get anywhere close to understanding it.
I think I understand bitcoin - and I'm not interested. Ethereum is new to me, but it looked very similar to something I'd seen years ago. The new craze of "initial coin offerings" look a lot like vaporware (same as most of the other coins, but with slight - sometimes very, very slight twists - like almost "sleight of hand" twists) and only promise to be "useful" in some way way in the future, after the people who take all the money for the coins use their millions to actually develop some sort of software/platform that will make billions of dollars in transaction fees because it's just so damned useful (according to the notes that they hashed out at Panera Bread on a napkin, before selling the coins to the public)...
Ooof.. already tired of thinking about it.
