What is the gap between professional singers and ordinary people?

Professional singers are called professional singers because they have undergone professional training, such as bel canto, such as bass singing, and some people specially teach them how to pronounce, while ordinary people sing more by their own feelings. With their natural voice and lung capacity, they can sing a high-pitched song with large lung capacity, and then the voice is better, which is more suitable for a song and sounds better. Unlike professionals, they will deliberately control to change their tone, size and sound level.