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.
For those of you who have not been paying attention to one of the biggest trends in investing and tech, cryptocurrencies are digital currencies using encryption techniques that regulate the generation of currency and verify the transfer of funds, operating independently of a central bank. Units of currency are created through a process referred to as mining.