A Mood is difficult to define, but moods are a common aspect of human experience. Depression is not about what kind of mood one is in.
Depression is about the absence of an emotional response capacity.
I hesitate to say that moods are a normal part of human experience. It is difficult to determine whether ones mood is normal are not. Such is particularly the situation with the person who experiences early onset of depression. First of all, one does not consciously know that he or she has a mood disorder. In the case of depression, one can grow up thinking that the absence of emotional responsiveness, or a certain listlessness or hopelessness is normal.