Getting Attached
When your baby is well attached it will feel better. This is the primary indicator, more important than how it looks. However, those supporting you will also be looking for visible signs of good attachment, including how much areola they can see.
The skin around your nipple is very individual. Some breasts have pale areola while others are quite dark. Some are small enough to completely disappear into the baby's mouth while others extend beyond the area touched by the baby's face.
What we are actually looking for is how much of the breast is taken into the baby's mouth. The areola is just a visual marker for this, not a functionality significant thing. If you can still see the areola above the baby's nose, that is not a concern. It is likely you can't see the area below the mouth as that will be well-covered by the chin.
When a baby takes a full mouthful of breast tissue, the nipple is in a better position. It should feel better but might still be tender if it is grazed or cracked from existing damage. Healing is supported by better attachment.