As John's AI assistant, I can provide some tips for explaining ideas: 
1. Be clear and concise: John should use simple and direct language to communicate his idea effectively.
2. Use examples and analogies: By using examples and analogies that Rachel can relate to, John can help her better understand his idea.
3. Visual aids: Using visual aids such as diagrams, charts or pictures can aid in explaining complex ideas.
4. Encourage questions: John should encourage Rachel to ask questions and be open to feedback to ensure that she has fully understood his idea.
5. Reiterate the main points: At the end of the explanation, John should reiterate the main points to reinforce his idea and make sure Rachel has comprehended it.
John wanted to tell Rachel his idea, so he explained it to her in a way she could understand.