I don't know about orphaned/UN-orphaned blocks too much, can you explain in simpler terms, or just tell me after how many confirmations a transaction cannot be unconfirmed?
This is a peer-to-peer system. There is no centralized server that is the authority of what has happened, and what has not.
Imagine for a moment, two miners both solve a block within fractions of a second of each other. One of those miners had included your transaction in their block, the other didn't.
Which block gets to be added to the blockchain?
Each of the two miners broadcasts the block that they solved to all of the peers that they are connected to. That means some peers on the network have seen the block with your transaction in it first, and other peers have seen the block without your transaction in it first.
The network is now split, with disagreement on which of the two blocks is the permanently "valid" block.
If the first block that your wallet received was the block that included your transaction, then your wallet will indicate to you that you have 1 confirmation. The other half of the network will still know about your transaction, but they will see it as "unconfirmed".
Each half of the network then continues mining on whichever block they received first.
If the other half of the network solves the next block first, then they will add it to their version of the blockchain. They will boradcast the new block to all of their peers. Some of those peers will be on your half of the network. Those peers will see that the new blockchain is longer than the one they are working on. They will immediately switch over to the new longer blockchain and the relay it to the rest of your half of the network. The entire network will see that this new chain is longer than the one that has your transaction confirmed. All the transactions that were confirmed in the same block as yours, which weren't also confirmed in either of the two blocks from the other half of the network, will become unconfirmed again and will need to continue to wait to be included in a future block.
This is how the network arrives at consensus. Anytime it splits, each half tries to make their half of the network into the "valid" one by being first to solve the next block.
With an average of 10 minutes between blocks, the odds are that most of the time two competing blocks won't be solved so close together in time, but it can (and does) happen.
Now, there is a possibility that when the network has split like that, each half of the network could each solve a block at nearly the same moment. If that happens, then there is a fork that is 2 blocks long, and each half is racing to be the first to solve the third block. It could happen again, and each half could be racing to solve the fourth block.
As you can perhaps see, there is no quantity of confirmations that result in a transaction that "cannot be unconfirmed". However, the odds against a race condition still existing multiply with each additional block:
Most blocks are not orphaned.
Occasionally, a 1 block fork is orphaned.
Rarely, a 2 block fork is orphaned.
Extremely rarely, a 3 block fork might be orphaned.
I'm not sure how many times a 4 block fork has been orphaned.
I haven't done the research, but my guess is that a fork more than 4 blocks long hasn't been orphaned more than twice in the history of bitcoin.
Note that an orphaned block doesn't necessarily result in a transaction becoming unconfirmed. If the transaction was confirmed in both forks of the blockchain, they it will remain confirmed regardless of which fork "wins".
Also note that, when a transaction does become "unconfirmed" due to an orphaned block, the transaction returns to the pool of unconfirmed transactions and is extremely likely to be re-confirmed in a block in the near future.
