The "Inner V" of your eye isn't a technical term, it's a makeup-application one that refers to the inner corners of your eyes. By adding a highlighter or brightener to this area (see the white shimmery shadow that creates a v-shape on Blake Lively's eyes), you can really make your eyes stand out.
Learning how to play up your inner v is easy. Simply use a gold, pink, white or cream highlighter, eye shadow or liner pencil and draw a horizontal V along the top to the bottom of the inner corner of your eye. Blend the product with your fingers and extend the color just under your lower lash line. This trick works wonders with all eye shapes, and it's especially effective when you are trying to give close-set eyes more balance.