"Kinda" is how it sounds when people say "kind of" fast. We tend to drop the "f" sound in the word "of" so it ends up just sounding like "kind'a". It's heard in conversational, colloquial English, but is normally written in novels when there is dialogue or in text-speak on social media as it is of course, not proper.

Yes, it is just the way people say "kind of" in conversation. As you can see from these sentences, sometimes it doesn't really have much meaning and is just used as a filler word like "like". ("I was like so happy to see her). I always tell English learners that some words like "kinda", "wanna" ("want a" or "want to"), "gonna" ("going to") are not considered "proper English" and you should probably avoid using them IN WRITING until you are very fluent and understand when to use them and when not to.

Kinda= kind of

KINDA means "kind of".