This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
... as well.

What are zero confirmation transactions?

Here’s a little refresher for those unfamiliar with how Bitcoin works. When someone sends you bitcoins, the
transaction is broadcast to all the nodes in the Bitcoin network. The mining pools collect these new transactions and temporarily hold them in memory. At this point we say that transactions are “unconfirmed” or “pending” inclusion in Bitcoin’s ledger ― the blockchain. Approximately once every 10 minutes a mining pool collects these transactions from memory, organizes them i...
read full book block explorer