Learn Hardcore Spanish (Spain): El conductor sale temprano para evitar el tráfico. - The driver leaves early to avoid traffic.

Conductor simply means “driver,” i.e. the person who operates a vehicle. It can refer to anyone driving a car, bus or truck—not necessarily a hired chauffeur. If you need the feminine form, it is conductora.

Which verb is sale, and what tense and person is it?

Sale is the third-person singular form of the present indicative of salir (“to leave” or “to go out”).
– yo salgo
– tú sales
– él/ella sale

Why isn’t there any preposition after sale? For example, why not sale de casa temprano?

Here sale is intransitive and is directly modified by the adverb temprano (“early”). You only add a preposition like de if you want to specify origin:
– Sale de casa temprano. (“He leaves home early.”)
But if you only mention when he leaves, you say:
– Sale temprano.

Is temprano an adjective or an adverb? Should it agree in gender or number?

In sale temprano, temprano is an adverb of time (“early”). Adverbs in Spanish do not change form, even though temprano looks like an –o adjective. As an adjective you could say “la clase temprana,” but as an adverb it stays temprano for everyone.