In this educational session of From Theory to Practice, Jim Schultz continues his deep dive into Delta by explaining how traders can use it as a probability gauge - the second most common application beyond the textbook definition of measuring option price movement. Delta serves as an excellent probability approximator in two key ways: 1. **Probability of expiring in-the-money**: This explains why traders typically select 30-35 delta strikes for short options strategies. The inverse (1 minus delta) indicates the probability of expiring out-of-the-money - crucial for premium sellers. 2. **Probability of touch**: Calculated as two times the delta, this measures the likelihood that a price level will be reached at some point before expiration, helping traders assess potential market movements.