What's the Real Deal with "Cognizable Offence" in IPC?

I'm trying to wrap my head around this but my textbook makes it sound like a joke. I mean who actually knows what this term means? A cognizable offence seems to be like a magic trick - suddenly police can arrest someone without a warrant, magic! But seriously, can someone please explain with a real-life example? Like, say, a traffic challan (family thinks I can get them out of it 🙄). Or maybe a street brawl? How do we know if it's a cognizable or non-cognizable offence? Help, someone, please!