What is a Vanguard Exchange-Traded Fund?

Could you please elaborate on what a Vanguard Exchange-Traded Fund (ETF) is and how it differs from other investment options? As a beginner investor, I'm interested in understanding the CORE features and benefits of Vanguard ETFs. Are they suitable for long-term investments? Do they offer diversified portfolios? What are the potential risks involved? I'd also like to know if Vanguard ETFs are managed actively or passively and how that impacts their performance. Your insights would be greatly appreciated.