What is confirmation?

Confirmation of the transaction is necessary to prevent the reuse of the same money.  As soon as the sender transfers the funds, the transaction enters the cryptocurrency network for processing and inclusion in the block.

It is the process of adding a transaction to the found block called transaction confirmation, one block includes one confirmation.

As soon as your transaction receives confirmation, the coins become available for further use.

The speed of confirmation depends on many factors, such as the workload of the cryptocurrency network itself, the amount of the commission indicated during the transfer, the speed of the Internet connection, the technical health of the resource where your wallet is located, etc.

Transactions that have not yet been processed and confirmed by miners are stored in the memory of nodes in the pool (mempool):

https://blockchain.info/ru/charts/mempool-count

While the transaction is stored in the pool (mempool), it is not visible in the Blockchain Explorer:

 https://blockchain.info, https://blockexplorer.com

Sometimes a transaction can be stored in a pool (mempool) for 6 to 48 hours.  On average, transaction confirmation lasts from 30 minutes to several hours, but sometimes it takes up to 6 days if the Bitcoin / Ethereum / Litecoin / Dash / Monero network is congested.