Coinbase requires you to link a bank account, or credit or debit card to your Coinbase account to purchase cryptocurrencies. Using a bank account allows for higher limits ($100/transaction, $2,500/week), but it also takes longer to verify transactions, so you will not see money in your Coinbase wallet for two to four days (depending on your bank). And when selling Bitcoin, once the sale is confirmed, it takes two to four days for the proceeds of that sale to show up in your bank account. With a credit or debit card, limits are lower ($200/week), but you can purchase digital currencies by simply transferring funds from that bank account to the site. For these transactions, Bitcoin shows up in your Coinbase wallet instantaneously. You can also sell Bitcoin to your PayPal account, effectively cashing out, as your Bitcoin will be exchanged for local currency. This transaction, too, is instantaneous.
Coinbase was founded in June 2012 by Brian Armstrong and Fred Ehrsam. Blockchain.info co-founder Ben Reeves was part of the original founding team but later parted ways with Armstrong due to a difference in how the Coinbase wallet should operate. The remaining founding team enrolled in the Summer 2012 Y Combinator startup incubator program. In October 2012, the company launched the services to buy and sell bitcoin through bank transfers. In May 2013, the company received a US$5 million Series A investment led by Fred Wilson from the venture capital firm Union Square Ventures. In December 2013, the company received a US$25 million investment, from the venture capital firms Andreessen Horowitz, Union Square Ventures (USV), and Ribbit Capital.