Not sure of what level of knowledge you seek and you may well need one of our experts here, but (like Obidiah), in simple terms, 'Induced' drag is that drag caused by the generation of a lift force, and a large amount of it is due to the energy 'wasted' in making the vortices which trail from the wing, rudder and tail tips. This has to come from somewhere and represents itself as a 'drag' force. Likewise the 'energy' required to change the direction of the air over a lifting surface to generate the lift is part of the 'induced' drag.
Depending on the level you seek you may not need to worry about the detail of up/downwash etc.