Sure, this refers to the ratio of thickness to chord, or if an airfoil is 10% it's thickness is 10% of the chord, or measurement from the front to back.
A wing that is 500 mm from the leading edge to the trailing edge, and it's a 10% airfoil, it would be 50 mm thick. Airfoils of the same section (or shape) with a greater thickness will stall at a slower speed, give more lift and drag, generally.