Confirmations Competing

"A transaction is not fully settled when it is first broadcast, because the network must include it in a block and confirm that block through consensus. If two blocks are discovered at nearly the same time, the network continues building on one chain and treats the other as an orphaned block, requiring its transactions to be processed again if they were not included in the accepted chain. Additional blocks make the record increasingly reliable, and Bitcoin delays a winning miner's ability to spend its reward until many more blocks have been added."