What does inversion refer to in terms of foot position?

Inversion refers to a specific movement in which the sole of the foot turns inward, toward the midline of the body. This action typically causes the soles of the feet to face each other, which aligns with the definition provided in the correct answer.

Understanding inversion is important for comprehending foot mechanics and how different movements can affect balance and stability during exercises. For instance, when performing certain physical activities or exercises that require agility and quick direction changes, the ability to invert the foot plays a crucial role in maintaining proper alignment and preventing injuries.

The other options describe various positions of the foot but do not align with the specific definition of inversion.