In psychiatry or psychology, professionals refer to an affective disorder as a prolonged emotional disturbance. It is a psychiatric disorder that has a profound central emotional component especially characterized by depression. When you speak of bipolar affective disorder, you speak of such a condition, but one that switches you between the extremes of mania and depression.
When you have bipolar affective-disorder, you will find yourself suffering from extreme mood swings, which range between acute euphoria mania and severe depression. In bipolar affective disorder, the depression you suffer from is as bad sometimes as major depression, which I must assure you is a very bad thing; and the mania can be mild or severe.
The manic phase of bipolar affective type of disorder can have you feeling unusually and unreasonably capable; like you own the world and that nothing can go wrong. It is worse because you tend to feel irritable when you want something and you cannot have it, and it may cause you to lash out at the people you love. Of course in this energized state, you are bound to have trouble sleeping and engage in rapid-fire speech that is heading you nowhere.
When you are suffering from the depression of bipolar-affective disorder, you are entirely the opposite. Things could get as bad as hallucinations and delusions, but often it begins with the weakness and listlessness that often is quickly followed by a sense of helplessness that makes it hard for people to be able to enjoy your company.