Is Optimism a real coin?

I've been hearing a lot about Optimism lately in the cryptocurrency space, but I'm still a bit confused. Can you clarify for me if Optimism is actually a real coin, or is it something else entirely? I've seen people talking about its potential and the technology behind it, but I'm not sure if it's something I should be investing in. Could you provide me with some insight into what Optimism is, and whether or not it's a viable option for cryptocurrency investors?