It can't be separated. Bitcoin and Blockchain or altcoins with Blockchain have an attachment and need each other.
The blockchain industry need all of them to grow, not only Bitcoin but Bitcoin is a backbone of this industry.
Blockchain becomes a ledger that will record every transaction made and the transaction is transparent and can be seen by anyone and cannot be deleted. Blockchain is like an Android system where applications run on that system.
It is not correct for all blockchains. Monero is a private and anonymous blockchain. Governments want to trace and break privacy, anonymity of Monero transactions but they have yet succeeded.
Bitcoin is arguably only one application of the blockchain system and there are many other applications ( Altcoins).
Each blockchain has different usecases and a cryptocurrency is part of one blockchain. Altcoins can have no usecases if they are scam coins.