"The eyes are the windows to the soul," is talking about how much the eyes can tell things about a person. If you look into someone's eyes, you can see hints of the things a person is thinking about. It's saying how much a simple look in the eyes can almost tell a person everything. You can tell whether a person is happy through the eyes, whether a person is sad through the eyes, and whether a person is upset or angry through the eyes.
"the eyes are the window to the soul" means that when you look into a person eyes you can see who they are and what there feeling.they say face expressions says it all but really the eyes do... your eyes tell you story