What is applied behavior?

Could you please elaborate on the concept of "applied behavior"? I'm curious to understand how it differs from traditional behavioral theories and how it's applied in practical settings. Specifically, I'm interested in knowing the key principles and techniques involved in applied behavior analysis, and how they can be used to modify human behavior in a positive and effective manner. Additionally, I'd like to know about the potential applications of applied behavior in various fields, such as education, business, and mental health.