One of the most common question I hear from people getting into the retro gaming world is: “What is sync?”. It’s a term that’s unfamiliar to your average gamer in all regions, as most people would just get whatever cable was the easiest to use and plug it into their TV without worrying about the exact signals inside. I did a decent job breaking sync down into layman’s terms as part of the RGB Guide here: http://retrorgb.com/sync.html
…but unfortunately, that page just scratches the surface of what csync actually is and how it differs from separated H&V syncs. Luckily, Ste from HD Retrovision has created a blog post breaking it down for the intermediate-to-advanced crowd. If you’d just prefer to buy the right cable and move along, these posts aren’t for you…but if you have even the slightest curiosity about how some of this stuff works, I strongly recommend you give it a read.