What's "not to mention" mean and when's it used?

Native speaker’s answer
Rebecca
"Not to mention" introduces an additional point that emphasizes the point already being made. So you can use it when you want to include an additional point to something you're saying, even if it's not the main point. Ex: I'm a big fan of Harry Styles. His music is amazing, not to mention his acting skills. Ex: I have so much work to do this weekend, not to mention cleaning my house, so I can't hang out.