Energy initially exists as potential energy. Electrical potential energy, chemical internal (potential) energy, nuclear energy, mechanical (gravitational) Potential energy, elastic PE etc.
When work is done by a force (in that field) or a reaction, then it is converted in to other forms. Energy cannot be created or destroyed. It can only be converted.
When a chemical reaction takes place, some internal energy is converted in to sound, heat, electromagnetic wave, electromotive force etc. When nuclear fission takes place nuclear energy from forces of attraction of charges & gravity are converted into kinetic energy, sound, heat radiation etc.
When a spring is compressed, kinetic energy is converted in to potential energy.
When physical matter with mass m is converted into pure energy form, then it is converted as E = m c² (c = speed of light). This is the energy that is inherent in a physical body.
When a body is burnt, the energy is released from oxidation of some elements and compounds in the matter and it is converted in to heat, and radiation.
When a electrical conductor loop (circular or rectangular) moves in a magnetic field, electrical potential difference is generated, then electrons get kinetic energy. That is the current.
When we change the current in a conductor loop then the conductor wire experiences force and torque, and the loop rotates generating mechanical energy.