A Block Hash or just Hash is a unique string of characters (numbers and letters) that identifies a specific block. Think of it as a fingerprint - if you have the hash, then a search of that hash on the block explorer will give you the corresponding block it relates to, with all the information in it.
For example, a Bitcoin Block Hash could look like this: 00000000000000000009c041277bfaed1a4a00a0838904f344d0fd1da2e984dc
And Safex Block Hash could look like this: ef43fd7f9963a457d4f0f68264398b5702e701df776d049c890ca517baad6dfc
Block Hash on Transparent Blockchains - Bitcoin Blockchain
If you visit any Bitcoin block explorer and paste your block hash, you will get the following information:
block number, size, version, merkle root, nounce, time, and many others. Below that you can see all the transactions that are part of that block, and if you click on some of the transaction hashes, you can see all the transaction information.
More about transaction hash you can read here.
Block Hash on the Safex Blockchain
On the Safex Blockchain, when you paste a block hash into the field, you will see, among other things: block hash and its height, previous block and following block number, timestamp, version, block reward, block size, nonce, total fees.
There’s no information in the Safex block hash to identify anyone’s private information, such as the the number of coins they have or how much or when they made certain transactions. All the confidential information is protected by ring signatures and stealth addresses which are the essential parts of the Safex privacy blockchain.