what is energy?

like a lot of scientific concepts, energy is hard to understand in a day-to-day sense, because, (1) it is called by a name that is a word in colloqual use but yet has subtle distinctions in meaning from how it is used colloquially and (2) because although it can be rigorously defined within a conceptual framework in a way that permits application to a variety of observable phenomena, it is not directly observable. the actual scientfic measurement that one makes is the closest thing to direct observation, but only because fewer layers of conceptualization separate the measurement from the experience of the measurement.  contrary to some opinions, science is not about direct observation... it is about honing the art of indirect observation.