I have a much better idea of the concept of "public key" vs "private key" now regarding cryptocurrency, namely Zcash (ZEC). The old Zcash wallet, zcash4win, stopped working. It's now winzec, which isn't working either. If I had backed up the private keys from my two public addresses in the old Zcash wallet, I would be able to access the approx .02 zec I have on the wallet. I knew the wallet was not very trustworthy so I would always send accumulated wallet zec to my Bittrex address, but would wait until I had accumulated .06 zec to do this. Also there is about .005 zec in the mining site wallet, which has to reach .01 before they pay out. So I lost about .025 zec because I only backed up the wallet file, and not my private keys.
1 zec currently trades at $243.21 so .025 zec is $6.08 cents. That's six bucks that goes "poof" except in the unlikely event that I figure out how to extract the private keys from the old wallet.dat. Since I started mining zec about a month or two ago I have made about $50 worth of zec. Zec is down off of a high around $400 recently, and before I started mining it got even higher than that. Strangely though it seems to have no official WIndows wallet, the main wallet being Linux.
Now using Jaxx wallet. The old zec4win was put together by some random dude but Jaxx seems to be better funded. I got into zec because it turned out to be easy to mine, and after getting burned by Electroneum. Electroneum was touted as easy to mine and it was, but never got accepted by an exchange besides Cryptopia. I sent my 65 Electroneum to Cryptopia and it disappeared. I wrote a report ticket. Two months later I get a response that my ticket has been solved and my 65 ETN will now show up in my ETN Cryptopia wallet. However as many thousands of people who have ETN on Cryptopia know, their online wallet has been "under maintenance" for weeks and my ETN never showed up. 1 ETN is now worth $.03 (three cents) so my 65 ETN are worth $1.95. As you can see I don't have a lot of money tied up in crypto (well unless you count my bitcoin which I mined). Mining ZEC isn't hard once you figure out how to do it. More importantly it is a real crypto-currency, not the dubious sketchy British Electroneum.