Just a couple of days ago, in a work call, someone asked me the difference between blockchain and blockspace.
Blockspace is a bit of a abstract concept. The capacity to fit transactions in a block.
Check out episode 44 for a overview of block limits.
Blockspace is a higher lever concept that refers to the overall capacity of the blockchain to process transactions and data, per block.
When we evaluate blockchains, looking from the blockspace perspective can be useful.
If the blockspace is secure, that means a blockchain has strong security and decentralization properties. There are less chances for hacks or exploits.
If the blockspace is highly available, that means the blockchain has more capacity and throughput to process more transactions.