Is the whole point that you buy and sell using cryptocurrencies and you don't have anything to do with $/£ etc?
Well the person themselves could certainly have a mix of both and do what they like, but the transaction itself would not involve the fiat system. Read the
whitepaper for a general explanation of its purpose.
What I am not clear on, though, is if you used a blockchain to buy something.
It's very simple. You have Bitcoin wallet software. The merchant gives you an address. You use the wallet software to send to their address, and the transaction later confirms. You're done.
dude do not be lazy and go on YouTube you'll all be shown and told
Explanations on there can be vague or contradictory. A BTC user needs more than vague analogies and such.