What is a Coincheck?

Can you explain to me what exactly Coincheck is? I've heard of it in the context of cryptocurrency but I'm not entirely clear on its function or purpose. Is it a platform for buying and selling digital assets? Does it offer any unique features or services that set it apart from other exchanges? Additionally, what kind of security measures does Coincheck have in place to protect users' funds and personal information? I'm interested in learning more about this platform and how it fits into the broader cryptocurrency ecosystem.