I always feel confused about the concept of wave. I don't know why we have to develop a term called "wave"? To me, wave made of particles oscillating up and down periodically. Is wave just a collection of particles or is wave an identity independent of particles? For example: Light a collection of photons Sea waves a collection moving water molecules Seismic wave a collection of soil particles Wave on a string is a collection of string particles But why do we say that electromagnetic wave is a collection of oscillating electric and magnetic field? Why not say that it is a collection of some particles? To me, field is an abstract idea(cannot be seen/touched) whereas particles exist in nature.