Gretchen Rubin's Four Tendencies is a framework that categorizes how people respond to expectations. The four types are Upholders, who meet both inner and outer expectations; Questioners, who question expectations and only follow those they find justified; Obligers, who meet outer expectations but struggle with inner ones; and Rebels, who resist all expectations. This model helps individuals understand their behavior and motivations, making it easier to create effective habits and achieve personal goals. By identifying their tendency, people can tailor their strategies for productivity and accountability, leading to improved outcomes in various aspects of life.