Each Monero transaction has a transaction ID linked to it.
This is a code used to track the transaction and ensure it has completed successfully.
Each transaction needs to be mined before it can show up in the recipient account. Monero transactions require a minimum of 10 confirmations before they can be considered completed.
You can use the transaction ID to check if the transaction has been mined successfully, by visiting https://xmrchain.net/ and typing in the transaction ID.
You will be checking to see that the transaction has a "Block" number and how many confirmations it has.