Instructs a node to attempt to fetch a specific block from a peer by its block hash.

How is this used?

You're collecting pieces of a historical map, but you're missing a crucial section that one of your contacts has found. You reach out to them to request this specific piece to complete your collection. Similarly, in the Bitcoin blockchain, if you're running a node and find yourself missing a specific block or you suspect your version of a block might be incorrect, you can use the 'getblockfrompeer' command to directly request this block from a connected peer by specifying its hash.