Bitcoin is one of several crypto-currencies which are exchanged generally outside of sovereign control and all electronically. In early 2014, a Bitcoin exchange named Mt. Gox filed bankruptcy in Tokyo and subsequently sought additional protection in the US by filing a chapter 15 bankruptcy petition. Just recently, the bankruptcy trustee in Tokyo has announced he will begin to pay back account holders in Bitcoin using a US based bitcoin exchange.
Dogecoin is another crypto-currency and is my personal favorite because of the mascot.
First, some background. Skip this is you are familiar with Bitcoin
Bitcoin is not a “coin” at all in the traditional sense. Rather, one bitcoin is essentially a complex mathematical code which is recorded on a public ledger as one bitcoin. That bitcoin has a two security keys which permit the bitcoin to be owned by (and transferred) by a person.