Poloniex was once the best cryptocurrency exchanges, before competitors like Bittrex starting offering superior services. Nevertheless Poloniex went through extremely fast traffic growth since the demise of its rival Cryptsy in 2016, and especially since the recent altcoin bubble of early 2017. Traffic has grown from 33 million monthly visits in November 2017 to 66 million in December 2017. Poloniex has the nicest trading interface out there, both for mobile and desktop users this will work wonders. Please note that because Poloniex is a pure "crypto" exchange, it is not possible to deposit government (fiat) currency. You'll need to first buy bitcoin elsewhere, and then deposit it to be able to tade. I've written a full analysis of Poloniex, further exploring the founders, users, security, fees, history, and alternatives.
Every single transaction made and the ownership of every single cryptocurrency in circulation is recorded in the blockchain. The blockchain is run by miners, who use powerful computers that tally the transactions. Their function is to update each time a transaction is made and also ensure the authenticity of information, thereby ascertaining that each transaction is secure and is processed properly and safely.
The User recognizes that the Ethereum Platform is under development and may undergo significant changes before release. The User acknowledges that any expectations regarding the form and functionality of the Ethereum Platform held by the User may not be met upon release of the Ethereum Platform, for any number of reasons including a change in the design and implementation plans and execution of the implementation of the Ethereum Platform.

In March 2017, various blockchain start-ups, research groups, and Fortune 500 companies announced the creation of the Enterprise Ethereum Alliance (EEA) with 30 founding members.[23] By May, the nonprofit organization had 116 enterprise members—including ConsenSys, CME Group, Cornell University's research group, Toyota Research Institute, Samsung SDS, Microsoft, Intel, J. P. Morgan, Cooley LLP, Merck KGaA, DTCC, Deloitte, Accenture, Banco Santander, BNY Mellon, ING, and National Bank of Canada.[24][25][26] By July 2017, there were over 150 members in the alliance, including recent additions MasterCard, Cisco Systems, Sberbank and Scotiabank.[27][28]

The user acknowledges and agrees that, to the fullest extent permitted by any applicable law, the disclaimers of liability contained herein apply to any and all damages or injury whatsoever caused by or related to risks of, use of, or inability to use, ethereum or the Ethereum platform under any cause or action whatsoever of any kind in any jurisdiction, including, without limitation, actions for breach of warranty, breach of contract or tort (including negligence) and that neither Stiftung Ethereum (i.e. Ethereum Foundation) nor Ethereum team shall be liable for any indirect, incidental, special, exemplary or consequential damages, including for loss of profits, goodwill or data that occurs as a result.