What's the difference between "selbst" and "selber"?
Both mean "self" or "myself/yourself/etc."
selbst: More formal, can also mean "even."
selber: More informal, common in spoken language.
Example
Ich habe das selbst gemacht. (I did that myself - formal)
Ich habe das selber gemacht. (I did that myself - informal)
Selbst ein Kind kann das verstehen. (Even a child can understand that.)