The term PRO AND CON is a phrase used to describe two opposing sides of an argument. It is derived from the Latin phrase 'pro et contra, ' which translates to 'for and against.' The third letter in the word CON is 'O, ' so the full phrase is PRO AND CON. This phrase is often used to describe a situation where two sides of an argument are presented, and each side has its own merits and drawbacks. It is a useful tool for analyzing a situation and making an informed decision.