The wave is a function that depends on both the time and the space. The wave equation is a differential equation whose solution is the wave. Is it clearer?

Concerning the style, I use the < div > environment to align the picture to the left and to the right.

I have read your post. Please add references. I am sure this will bring you much more upvotes :D The post may also be a bit long for many people (but for me it is ok).