In the case of bitcoin, the blockchain is the technology that enables its movement from person to person.
It is the public database of all transactions.
It’s unique to a specific currency. Currencies do not share the same blockchain.

A block explorer is a program or website accessible through a compatible browser that allows a user to search and navigate the blocks of a blockchain, their contents and their relevant details.
We use block explorers daily to identify when funds have hit customer wallet addresses, verify transaction amount,s identify any fluctuations and more…
Some example of block explorers (btc):

• Blockcypher (immediate notification at zero confirmations).
• Blockchain.Com (shows btc conversion value in different currencies)
• Blockchair
• Insight.Is
• Oxt.Me

Bitcoin mining is the process of validating bitcoin transactions and adding the records to the bitcoins public ledger.
The blockchain serves to confirm transactions to the rest of the network as having taken place.
Miners confirm transactions with mining software and add them to the blockchain.  Miners get paid in bitcoins for completing this and that’s how new bitcoins are generated.