The block chain is
the key element in how Bitcoin functions. If you read more about how Bitcoin works (specifically transactions), you should start to understand why the block chain exists.
In this paper, we propose a solution to the double-spending problem using a peer-to-peer distributed timestamp server to generate computational proof of the chronological order of transactions.
Bitcoin transactions are sent from and to electronic bitcoin wallets like Blockchain
"Blockchain" is not a wallet, "blockchain" is the decentralized public
ledger journal[1] that keeps track of transactions and ensures an order between them.
Are you maybe refering to the service called "blockchain.info"?
, other in market and are digitally signed for security. Everyone on the network knows about a transaction, and the history of a transaction can be traced back to the point where the bitcoins were produced. Keeping record of transactions will help you to see how and when you have used it or traded it
You didnt read what danny wrote above did you?
[1] See the post by teukon[2] below for definitions of both words and why journal is the better word here.
[2]
https://bitcointalk.org/index.php?topic=1294531.msg13301043#msg13301043