A free tool
Flipgrid allows students to record simple videos or audio explaining their understanding. Teachers can give private feedback or public peer feedback is also an option.
I have used Flipgrid extensively to encourage pupils to respond and explain their understanding as well as speaking in a foreign language. They can record as many times as they like and submit when they are happy, get peer feedback and also screen record. As a result, I am able to give students my full attention and quality feedback as I can watch on repeat if needed