What term describes the extensive, task-specific knowledge that experts possess?

The term that best describes the extensive, task-specific knowledge that experts possess is "expertise." Expertise encompasses a deep understanding and mastery of a particular domain or field, developed through extensive education, practice, and experience. It implies not just familiarity with concepts or techniques, but also the ability to apply this knowledge effectively in real-world situations.

While "skill" refers to the ability to perform tasks competently, it does not inherently convey the vast depth of knowledge that experts possess. "Experience" indicates the accumulation of knowledge through direct involvement, but does not specifically highlight the level of understanding or specialization associated with expertise. "Proficiency" denotes a competent level of skill, but again, it may not fully capture the comprehensive and nuanced knowledge that characterizes an expert's capability in a specific area.

In summary, "expertise" stands out as the most accurate term for representing the profound, comprehensive knowledge and ability that experts have in their specialized fields.