What are prime numbers for dummies?

Hello there, I'm curious about something that might seem simple but can be quite complex for those not in the know. Could you explain to me in simple terms what prime numbers are? Maybe you could start with a basic definition and then provide some real-life examples to help me grasp the concept better. I've heard they're important in cryptography and security, but I'm not sure how they work. Could you also touch on that aspect, making it as easy to understand as possible? Thanks in advance for your help!