What is the difference between a tunnel and a VPN?

I'm curious about the difference between a tunnel and a VPN. Could you please elaborate on this topic for me? I've heard both terms used interchangeably in some contexts, but I'm not quite sure if they refer to the same thing or if there are distinct differences between them. Could you explain what a tunnel is and how it differs from a VPN? I'm interested in understanding the technical aspects as well as the practical applications of both concepts. Thank you for your assistance in clarifying this matter for me.