An anxiety is a worry about future events and fear is a reaction to current events. It is a state of apprehension, uncertainty and fear resulting from the anticipation of as real or imagined impending threats. In this regard, anxiety is caused by behaving in an apprehensive manner, such as worrying, imagining the worst, and fearing the worst.
An anxiety attack is a high degree stress response activated by either overly apprehensive behavior worrying fearing something really bad may happen or by the involuntary action of an overly stressed body.