A cryptocurrency is a digital coin, designed to be transferred between people in virtual transactions. Cryptocurrencies exist only as data and not as physical objects; you cannot actually hold a Bitcoin in your hand or keep Ethereum in your safe. Owning a Bitcoin means you have the collective agreement of each and every computer on the Bitcoin network that it is currently owned by you and – more importantly – that it was legitimately created by a miner.

The existence of market makers (e.g., Virtu Financial) refutes a common assertion about futures—that there‘s always a loser for every winner, that it’s a zero-sum game. It’s true that derivatives like stock options and futures are created in matched pairs—a long and a short contract. If two speculators own those two contracts the profits on one side are offset by losses on the other but market makers are not speculators. In general, they’re not betting on the direction of the market. They act as intermediaries, selling to buyers at the higher ask price and buying from sellers at the lower bid price— collecting the difference.

The Fund generally does not expect to invest directly in futures contracts, option contracts and swap agreements (“Bitcoin Instruments”). The Fund expects to gain exposure to these investments by investing a portion of its assets in the ProShares Cayman Short Bitcoin Futures Strategy Portfolio, a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Subsidiary”). The Subsidiary is advised by ProShare Advisors, the Fund’s investment advisor, and invests directly in Bitcoin Instruments. Unlike the Fund, the Subsidiary is not an investment company registered under the 1940 Act. The Fund’s investment in the Subsidiary is intended to provide the Fund with exposure to commodity markets related to bitcoin in accordance with applicable rules and regulations. The Fund will invest up to 25% of its total assets in the Subsidiary. Except as otherwise noted, references to the Fund’s investment strategies and risks include the investment strategies and risks of the Subsidiary.
Futures contracts derive their value from an asset and more or less follow the movements of the underlying commodity, in our case: bitcoin. They ultimately settle at price of the commodity in the future on a particular exchange, or an index that represents a basket of prices at different exchanges.  So if you have a weekly future's contract and you don't want to sell out of it on the market,  then it will expire at the price at a specific time when Friday comes and if you want to maintain your position you must re-open on the new contract period. In the weekly example, if a contract is issued at April 14, 2017, it dies on April 21, 2017. If you buy the contract at a price of $1,100 and you don't sell it for the whole week, and the price ends on April 21 at $1,200, then you profit.
* The “Fund Complex” consists of all operational registered investment companies under the 1940 Act that are advised by ProShare Advisors LLC and any registered investment companies that have an investment adviser that is an affiliated person of ProShare Advisors LLC. Investment companies that are non-operational (and therefore, not publicly offered) as of the date of this SAI are excluded from these figures.
Note that you could just keep bitcoin on CryptoFacilities waiting to make the trade so you don't have to wait to move the bitcoin you bought over. This is called see-saw arbitrage model, where you keep funds on both exchanges to avoid having to wait. This is fine, but you can't ignore that there is extra capital being used in the play, so it affects your rate of return and capital utilisation. We will not use this method, we will do a full, complete, legitimate arbitrage process.