You’re not dumb, kbin isn’t as big of an instance as Lemmy or Mastodon so kbin would be in the “other similar platforms” category. If you like you can imagine the kbin logo and a green plus sign in-front of the Lemmy logo. It is of note that on kbin the “boost” is the true upvote button. The upvote button does show popularity but it won’t “boost” the posts to the front page.

For simplicity, you can just add Kbin.social to the Fediverse cloud in the second row. You’ll see all the same content that we all see, but with a different coat of paint.

Think of it like viewing the Internet with different browsers chrome, Firefox, or Safari.

There are some functional differences to KBin, like the ability to boost, which is like a Twitter retweet, but without getting into the weeds on that stuff, it really is just the same thing with a different interface.