Approach-avoidance conflict refers to a conflict arising when the same choice has both desirable and undesirable features; one in which you are both drawn to and repelled by the same choice. It arises when a situation has both a postive and negative features.
Other /More definition:
Approach-avoidance conflict refers to conflict involving a single choice that has both positive (approach) and negative (avoidance) properties; being attracted to and repelled by the same goal or activity. Moreover, it is a conflict in which a choice must be made about whether to pursue a single goal that has both attractive and unattractive aspects. According to Lewin, the type of conflict that occurs when a person is attracted to and repelled by the same goal at the same time.