What does 'time to propagate' mean in a blockchain network?

Time to propagate is how long it takes for new data — like a transaction or a block — to spread from one computer to every other computer in a peer-to-peer network. In a peer-to-peer network, computers (called nodes) share information directly with each other rather than routing everything through one central server; when a node receives new data, it forwards it to its neighbors, who forward it to theirs, until the whole network has a copy. How quickly this happens affects how confidently a network can add new blocks, because a block cannot be safely built on until enough of the network knows it exists. For a beginner, the takeaway is simple: faster propagation means the network reaches agreement sooner, which is one reason block speed and network size matter in blockchain design.