How do I read the blockchain?
You are mistaken.
That link does not show you "the blockchain". That link shows you a web page created by a private company that has chosen to name themselves "blockchain.info". blockchain.info is NOT "the blockchain". That company collects their own copy of the blockchain (as well as other information from the bitcoin network) and then interprets that information and creates web pages and charts that attempt to explain what they think is happening. They aren't always correct.
Again, that link verifies only what the company called "blockchain.info" has interpreted from the blockchain. In this case it appears that they've done a misleading job of showing you some of the technical details behind how bitcoin transactions work at the protocol level, but a pretty good job of interpreting that technical information into concepts that might feel more familiar to users.
What you see there is only 1 transaction. On the left it shows the addresses that previously received the outputs that are being spent by the transaction and what the value of each of those outputs was. On the right it shows the two addresses that received the value that was supplied to the transaction and how much of that value was received by each address.
I assume that 1NybeKPyqVv8d9brkSTubgk5NynJy3h4hw is your address. It looks like the transaction spent two outputs valued at 0.119 BTC and 0.3017804 BTC for a total value supplied to the transaction of 0.4207804 BTC. Of that value, 0.38603733 BTC was assigned to an output with your address. That left 0.03474307 BTC unaccounted for. The transaction assigned 0.03424307 BTC of that remaining amount back to the address 19Kwfve8NLCnu6KJoAG2Jhg1knWmgTchEu (the same address where the value came from). The last remaining 0.0005 BTC that are not accounted for in the transaction become transaction fees for the miner that first placed the transaction into a block on the blockchain.
Can you tell me... is this from the perspective of the sender and are both transactions from the same sender?
It is only 1 transaction, and it is from the perspective of blockchain.info's interpretation of the transaction. The transaction was supplied with value (which can be seen on the left) and re-assigned that value to new addresses (which can be seen on the right).
What does the /tx/ in the URL stand for? Transaction?
Yes.
I usually see the /address/ URL and I'm not used to this one.
Then you are usually looking at blockchain.info's interpretation of what activity a given address has had on the bitcoin network instead of looking at blockchain.info's interpretation of a single transaction.
Also, when it reads "unspent" I'm assuming that the blockchain has tracked that I have not spent the BTC yet.
More specifically, the blockchain.info company has not yet seen any transactions on the bitcoin network that spend that specific transaction output.
If they had seen such a transaction, they would have changed the label to "spent" even if the transaction was not yet in the blockchain.
Is there a way to further track which address the money was sent to once I spend it?
Where it was sent to? That depends on what you mean.
It is possible to see what transaction is funded with those bitcoins. It is therefore possible to see each of the outputs that are created by the transaction and how much value each of those outputs receives. If the outputs are standard P2PKH or P2SH outputs, then it will be possible to see what address those new outputs will be associated with. If ownership of any of those addresses is known, then it would be possible to know who the bitcoins are sent to.
What if I spend small portions of it... how does that get tracked?
At the protocol level, you can't spend small parts of a transaction output. You have to spend the entire output all at once. Therefore, your wallet software will create a transaction that spends the entire 0.38603733 BTC output to fund the transaction. It will then create an output for this new transaction and assign the small amount you are sending to this output. The output will have the address you are sending to. Then the wallet will subtract the transaction fee (if you include any) from the remaining value. If there is any value remaining after that, the wallet will create another output and assign the remaining value to it. This second output will be assigned to an address that your wallet has control over. Depending on the wallet software that you use, the wallet might create a brand new address that it doesn't tell you about, but it keeps track of internally, or if might re-use an address that you have created in the wallet in the past.
