The phrase "whats-what" is typically used to refer to knowledge or understanding of a certain subject or situation. There are several synonyms that can be used to convey this same meaning, such as "know-how," "savvy," "understanding," "expertise," or "acumen." Each of these words suggests a level of comprehension and mastery that allows for effective decision-making and problem-solving. Other related synonyms include "aptitude," "insight," "proficiency," and "competence." Whether used in a personal or professional context, incorporating synonyms for "whats-what" can help to clarify one's level of understanding and establish credibility and authority in a particular domain.