The leg position will vary with couples but usually she has one under his and the other leg over him. The bottom leg is stretched down between her partner's legs. He's kneeling and thrusting into her vagina while he holds her ass cheeks apart or lifts her top thigh with one hand. She holds a wand vibrator under one of the pillows with her top hand because she is lying on her side. I focus on what I'm feeling instead of watching my partner.
Men however are such visual creatures they want to look whenever they can.
For me, the feeling of penetration in this position is exquisite and very intense. After all, we are human animals. This position gives the deepest penetration so a man must be gentle and not shove an oversized cock in up to the hilt. This position is a bit difficult if both partners are on the bed due to the long handle of a wand vibrator. But my lover discovered that standing behind me while I was kneeling on the edge of the bed made penetration much easier and effective.