The block explorer has long been one of the most important applications in the Bitcoin ecosystem. The blockchain’s ingenuity and the the massive computer power backing it make it the perfect financial ledger, but its sheer size and programming language make it unreadable to normal human beings.
Blockchain.info fixed that in 2011 with the first real block explorer available to the public. All 70+ million transactions and every Bitcoin address published to the blockchain are indexed and easily-searchable, with a simple user interface that almost anyone with a home computer can understand.
This has saved us all from a lot of tedious counting, allowing everyone to see any balance or movement of funds. It spurred a remarkable innovation in accounting–some Bitcoin exchanges are now publicly-auditable, and new systems like BlockTrail go even further at the expense of privacy–but as the blockchain advances, its explorers are lagging behind.
Crypto’s not just for currency, anymore. Colored Coins lets us turn bitcoins into smart property, and Counterparty and Omni go even further to let us include smart property and contracts, as well. Most “Bitcoin 2.0” systems like these make use of the Bitcoin protocol’s OP_RETURN feature, which is ignored by the likes of Blockchain.info; Coin Secrets