What does this warning (Your branch isn't protected) from GitHub mean?

I have a warning on a particular GitHub repository that states:

Your main branch isn't protected

Protect this branch from force pushing or deletion, or require status checks before merging.

1. Does this mean that anyone can just delete my main branch?
2. Or, does this mean people in my "group" that have access in the first place are able to delete my main branch? Thus, if I have no group of devs (I'm the only one) then the repo is protected by default?

Is There Basic Protection?

Isn't the repo protected by the fact that I have to sign in to push to it, meaning that someone would have to be able to sign in to the repo to delete or push against it?

The message means that contributors can force push and delete your branch. You would need to grant access to make someone a contributor.