Bitcoin transaction is fast because nothing impossible in technology. If someone gives you a bitcoin, you can easily convert it into something. In bitcoin transactions, it needs some of our real information to verify our identity.
Bitcoin transactions are fast when I buy something from Internet sitting on the chair front of my computer
but is extremely slow when I wait in the cashier of a supermarket with 10 other people behind me expecting to pay with cash or their debit/credit cards.It depends. If the transaction value is below $30, and you include a more than decent/appropriate fee, then it will most likely get accepted without any confimations. But if you're stingy on the fees, or your transaction value sits well above $50, then you'll surely be forced to wait for at least 1 confirmation. But then again, in this regard, I don't consider Bitcoin to function very well. It's great to complete online purchases, but not when it comes to completing payments in physical stores. Especially when it comes to larger amounts as you'll be forced to wait for at least 1 confimation.