The help section of Caching -> Configuration -> Caching Level says:
Note: By default, Cloudflare does not cache HTML content. You can create a Page Rule to cache static HTML content.
I have no page rules set yet. But when I goto Analytics, I see there are 600+ cached requests. Anybody know what happened here?
As the note says "By default, Cloudflare does not cache HTML content.". That means your .html files are not cached but other assets like images, javascript or fonts are.
Here a list of filetypes that will be cached by default:
https://developers.cloudflare.com/cache/about/default-cache-behavior#default-cached-file-extensions