Bitcoin is peer-to-peer digital cash that’s not issued by any central authority.
An exchange-traded fund (ETF) is an investment fund traded on stock exchanges, much like stocks. An ETF holds assets such as stocks, commodities, or bonds, and trades close to its net asset value over the course of the trading day. Most ETFs track an index, currencies or commodities.e.g gold ETFs track physical bullion gold price. Crude Oil ETFs track the market price of the oil barrel.
Buying shares of Bitcoin ETFs should be a great way to take advantage of the volatility of this innovative digital commodity without getting involved in bitcoin trading directly. buying, selling and storing bitcoin in a secure way can be challenging even to tech-savvy individuals.
Bitcoin wallets are constantly targeted by hackers and are also vulnerable to physical and electromagnetic damages. Even “brain wallets” (a method in which all the wallet code is memorized by the owner of the wallet) have been cracked by advanced algorithms and supercomputers.
As for today, there is no certified Bitcoin ETF anywhere in the world.There’s a number of bitcoin ETFs that are going through the regulatory approval process
Winklevoss bitcoin ETF- The Famous Winklevoss brothers are the main ambassadors and visionaries of the bitcoin community lobbying for the approval of their Winklevoss Bitcoin Trust ETF (NASDAQ: COIN) by the SEC.

The SEC will make a decision on a proposed bitcoin ETF by March 11.
The two main challenges for establishing a Bitcoin ETF are
1)What should be the reference for bitcoin spot price?
2)how to securely store that bitcoin?