Sign up vs Sign in?

Hi there,

Can someone explain the difference between sign up and sign in? As shown in image attached.

And how to remove either one of them so as not to confuse users.
Thank you

There is no difference

“Sign Up” only appears if your app allows anyone to sign in. If you restrict access to your app by making it private access, users will only see the 'Sign in" button because they can’t “Sign up” to join it.