This short video explains Child-Pays-For-Parent (CPFP), a way to speed up a Bitcoin transaction you are waiting to receive: How Child-Pays-For-Parent works.
What the video covers
If you receive bitcoin and the transaction fee was set too low, its confirmation can be delayed. Child-Pays-For-Parent is a technique for getting it confirmed sooner.
If your wallet software has coin control, you can spend the unconfirmed transaction by sending that coin to another address in your own wallet. This creates a child transaction from the original one, the parent.
Set the fee on the child high enough to make up for the low fee on the parent. Miners cannot confirm the child without confirming the parent as well, because the child is not valid until the parent is on the blockchain, so they include both in their block.
To work out the fee for the child transaction, use the CPFP Calculator. For a worked example, see Child Pays for Parent and How to use the CPFP Calculator.