Hand texturing is rolling and molding a bit of soil between your fingers to determine texture, which is a proxy of particle size distribution (e.g. sand, silt, clay percentage). Texture lets you know soil drainage and such.

You texture each horizon to get an understanding of the profile (whole vertical slice of soil, comprised of several layers).

Since the soil slowly dries out your hands, they get pretty rough by the end of a day (or 12, 14, or 21, in my case)