Is online mining legit?

Could you please elaborate on the legitimacy of online mining? I've heard various opinions about it, and I'm curious to know if it's a reliable and secure way to earn cryptocurrencies. Are there any risks involved? How does it work, and what are the essential factors to consider before engaging in online mining? Also, could you provide some examples or testimonials from those who have tried it successfully? Thank you for clarifying this matter for me.