Let's break it down:
* Le: This is the polite form of "you" in Spanish, used when addressing someone respectfully.
* gustaría: This is the conditional form of the verb "gustar" (to like). The conditional tense is used to express a polite request or offer.
* a usted: This phrase emphasizes politeness, literally meaning "to you."
* un bolígrafo: This means "a pen."
So, the whole phrase is a polite way of asking someone if they would like a pen.