DannyHamilton, wish we could all be as patient like you

Say a friend sells me a paper wallet, how can I make sure that the wallet has the balance printed on the paper? What online service or software can I use to import that wallet and start using it?

Another issue... there is a ton of explanations of how the bitcoin system works. But they are all very simple and not very technical. Google is flooded with simple to intermediate guides that give a very good picture to how it all works, but there are no details. It's hard to find "good" results (or ask the correct question) in google to more technical questions since google ranks on top all the simple explanations (since they get the most hits and are most popular) and the problems is that all questions i ask google have the simple answer.

To really know how it works, you have to be a programmer, and read the source code of some mining software, since there are no guides that I found that explain, for example, on what data hashing is performed or some of the other questions I asked in the beginning...

kokjo, no, that's not what I am saying (and I would never pay a teacher who calls his students "stupid"). I am saying that the bitcoin system is not a simple system. The concept it very well understood but the details are very complex. The questions I asked helped a lot of other users (who are maybe ashamed to ask?) to understand.
I am sure you can find much dumber questions on this forum. And I don't think the reply is that the asker is stupid.

DannyHamilton, thank you for all your answers! Things are a lot clearer now.

kokjo, thank you for the fucking links I did read those, but I am a slow learner i.e., a NEWBIE!

Another question. The SHA256 hash can run on any size of data since it divids the data into 512 byte blocks.
What exactly is the input to the SHA256 hashing algorithm? Is it something constant in size? Does the hash rate have any correlation to the  algorithm  e.g., the rare will be twice lower if SHA512 was used?

Why the size of a transaction is not a predefined size? Isn't a transaction's content is a pair of wallets and the sum transferred?

So why is it so hard to calculate a new block? Why does it take so much computing power? Is it due to the number of times this has to be repeated? The hash rate means how many times this process can be be repeated in a second?
How many unconfirmed transactions can be selected? Does it affect the hash rate? I mean, if the computer selects 1 transaction or 100, does it have any meaning?

Thank you for the detailed explanation!

Now, what exactly happens during mining? The computer generates random data, calculate its hash and if the hash is valid, the generated data is considered a valid block?

So how exactly a block is added to the chain? Why some blocks have very few transactions while others have a many? What does it mean that "a new block is discovered"?
I still did not understand the relationship between a miner and transaction confirmation.

DannyHamilton, I expect it to be THE mainstream payment system i.e., it will replace credit cards. But I don't see how it can happen with this slow confirmation mechanism...

That's only Paypal. What about the rest of the credit card industry? Banking industry?

I did some reading but I still can't grasp the relationship between transaction confirmations and miners... What is a confirmation exactly?
I got it that each transaction is written to the blockchain to the current block and I know that miners generate new blocks. But after it is written, can it be removed if it's not valid? Where exactly in the blockchain does it say if each transaction is confirmed?
When a new block is 'found' by the miners, who checks if its valid or not? who/what decides to add it to the block chain? Do miners generate empty blocks which transactions are later appended to?

Would be happy to get a good explanation (since what I read in the wiki, only raised more questions...)

Is it correct to say that the system as it is now is not capable of large scale eCommerce where tens of thousands of transactions need to be processed each second? If that is the case, when will it be ready?

Hi, I am new here and already did a lot of reading on the bitcoin. One of the main issues I can't understand is why confirmation takes so long (yes, 2-3 minutes is a LONG time, not to mansion 6 confirmations which can take hours). In today's eCommerce system, when I pay for something, confirmation is instant i.e., I click "confirm" and I am done and can continue about my business.
With bitcoin, how does it work? When I pay to a certain wallet, after how long can I be "sure" the payment arrived? How long will I be hanging in the air until the transaction is complete? What if I choose to make the transaction without a miner's fee? What fee will make the confirmation instant?
If I take it a bit further into the future and want to pay for my groceries in the supermarket, I can't hold the line waiting for a confirmation...