Great question! There is a slight difference between the two because when shouting you have to use words. Whereas yelling doesn't have to be words, it can be a loud sound or loud cry. Here are a couple examples: "We had to shout to each other to be heard over the music playing at the party." "The dog was yelling out in pain after it had been bitten by the other dog." I hope that helps! :-)

They could be.., it would depend on the situation, but 'yell' would be much louder than 'shout'.

Yes, to shout and to yell are synonyms.