Femoral (and preanal) pores are a row of small openings on the underside of a lizard's thighs that are noticeably larger in mature males — one of the most reliable ways to sex many lizards.
In species like leopard geckos and bearded dragons, prominent, waxy pores plus (in geckos) a hemipenal bulge mark a male; small, flat pores mark a female. They only become clear once the animal is grown.