What is the primary function of a nail buffer?

The primary function of a nail buffer is to smooth and shine the nail surface. Nail buffers typically have varying grits; the finer grits are used to create a smooth finish, while the coarser grits can help remove minor imperfections on the nail surface. By using a buffer, a nail technician can enhance the natural shine of the nails without the need for additional products or nail polish. This process not only improves the appearance of the nails but can also help maintain their health by promoting a polished look.

The other options, such as removing dirt or cutting the nail, involve different tools and methods, and applying nail polish is a separate step entirely that aims to enhance the nail's color rather than its texture or shine. Therefore, the focus on smoothing and shining aligns perfectly with the intended use of a nail buffer.