The document discusses the definition of "essential job functions" under the Americans with Disabilities Act (ADA) and California Fair Employment and Housing Act (FEHA). Both laws prohibit disability discrimination and require employers to provide reasonable accommodations. The laws also require employers to determine the essential functions of each job in order to prepare job descriptions, handle accommodation requests, and determine if accommodation is needed. The document defines essential functions as fundamental duties that the position exists to perform or that are highly specialized. It provides examples of evidence to consider a function essential and notes that marginal functions are not essential.