"Le" is used for both third person singular (masculine and feminine), and "les" for both third person plural. In English, its equivalent involves the preposition "to".
Yo le pregunté algo. --> I ask something to him (or I asked him something)
Nosotros le dimos un regalo a ella. --> we gave a present to her.
Ustedes les enviaron una carta. --> You guys sent a letter to them.
If want to emphasize the gender of the person, you just have to add "a él" (in case of a guy), "a ella" (in case of a girl), "a ellos" and "a ellas".