Do I Need To Be Filling In "Post Tags" or "Excerpt" Area When I Have All In One SEO

I'm still very confused about the function of the All In One SEO. As I do each post, should I be filling out the "Post Tags" section or the "Excerpt" section as well as filling out the All In One Seo section?

If someone could please clarify this for me, I would be very grateful.

 

I am wondering the same thing...I hope someone answers..It's confusing me!