These are two systems that allow you to change the commission paid on a transaction, usually to increase it and thus get the transaction to its destination sooner. Not all wallets allow this, you can try one of these: Blue wallet, Samourai wallet, Electrum, or Green wallet.
Replace by Fee (RBF)
This option is usually applied by whoever sends the cryptocurrency. What is done is to replace the original transaction with one that has a higher fee.
Child pays for parent (CPFP)
This second option is usually applied by the one who receives the cryptocurrency. In this case, the one who is going to receive the cryptocurrency generates a new transaction with a higher commission than the original one.