Hack The Box provides hands-on cybersecurity labs where you practice penetration testing against realistic targets. You get a virtual machine to attack and a set of challenges that range from beginner to expert. The platform covers web exploitation, network security, cryptography, reverse engineering, and more. Each challenge includes a flag you submit for points, and there's a global leaderboard for competitive players. The community writes walkthroughs and discusses approaches, which makes it a good learning environment even when you get stuck.

It's used by security professionals to sharpen their skills, by students preparing for certifications, and by companies for team training. There's a free tier with a limited set of machines and a paid subscription that unlocks more content. It's not a replacement for formal education, but it's one of the most practical ways to learn offensive security by actually doing it.