Traditionally taught, it is extremely complex. In simple terms, energy is present whenever anything has a change in state, whether that change is size, shape, location, movement, temperature, or structure. All changes, observable or not, are the result of energy in some form. Some forms of energy require an expenditure of energy to get started. If the result produces more energy, the object had potential.
Nuclear power is an example.
Objects moving have kinetic energy that can be transmitted to other objects. The seasons are caused by different amounts of energy being available from the sun. Life adapts to these changes. There are many kinds of energy. Different types of energy sources can produce the same outcome.