If you’re not familiar with mesh, this is an open knitting style that creates a pattern of interstices within the sock. These interstices allow your foot to breath, mesh being mostly used for sports such as
cycling,
running – and in some cases
hockey – where your foot is involved in an almost-mechanical repetitive effort (contrary to sports such as basketball requiring abrupt running back and forth as well as stops).
Mesh areas are typically located on top of the foot, used for ankle, no-show socks and can be knitted in any color.
As you can check on the picture below featuring a blue sports sock. the knitting difference between the mesh area and the rest of the sock is pretty obvious.
customized blue sport sock with mesh