The difference between This is about helping people with their problems. This is all about helping people with their problems. Is the amount of emphasis given to the utterance. It's very similar to the difference between: He is a big boy. He is a very big boy. The second sentence puts more emphasis on the fact of being big. Similarly "This is all about helping people with their problems." puts more emphasis on the action of helping people with their problems. It doesn't really change the meaning, just the emphasis. The same is true of the colloquial expression "What are you all about?", which basically means "What kind of things do you like to do?". The question has more emphasis than "What are you about?"