Metamask and kraken are ethereum wallets which can be used for storing, sending and receiving ethereum. Coinbase is a bitcoin exchange which can be used for buying and selling ethereum and bitcoin. Metamask is more of a chrome plug in which provides you a convenient interface built in with the ethereum wallet. This can be used to send and receive cryptocurrencies through your browser on desktop. Kraken is a more robust platform which also provides an API for connecting to your application. Coinbase is more of an ethereum and bitcoin exchange. You can buy and sell ethereum from there. Coinbase also provides an API for sending cryptocurrency from your application. Source cheap essay help online