A compare and contrast essay should identify complex details. Simple, basic, and unimportant details are all things that the reader can either figure out on their own or won't even need to know. Talking about the complex details really allows you to address all the points on what makes these two topics different from one another and what makes them similar.
because a subject is a part of a sentence that contains the person or thing performing the action (or verb) in a sentence so here the subjects are my friend and I