Not "a blockchain", since e.g. Hyperledger Fabric and other blockchains do not have the sha256 hashing and proof of work parts.
But "the" blockchain, as in Bitcoin blockchain, the most infamous one.
Title is misleading, but blog post is clear in being about Bitcoin.
Sure but how is this distributed?
Does every device hold the chain of blocks?
the joke i like to make:
it's a linked list with an O(exp(n)) append cost and a O(r*exp(n)) rewrite cost where r how many from the tip you wish to rewrite.
other notable: the 32 bit nonce is exhausted very quickly with modern mining systems, so they roll the timestamp forwards and backwards by a limited amount, add, remove and reorder transactions and iirc twiddle some bits in the coinbase (the first transaction the miner is allowed to add to the block to pay for the mining) to twiddle the merkle root.
the implementations of the mining systems are actually pretty cool. the host will compute the first rounds of the compression function for the first 32 bytes, and then hardware acceleration will take over for the open hash for the remainder which includes a host computed merkle hash and 32 bits of nonce + 32 bits of timestamp (with some maybe 8-10 bits of entropy to play with). so the host computes these new merkle hashes and partial sha2 sums, but then farms out the open hash state to the hardware to spin and check on timestamps and nonce values. (although newer stuff may need to compute the merkle hashes in hardware too)