It's a common Spanish phrase used when you're promising to send something to someone.
Here's a breakdown of the words:
* O: This is a conjunction that can mean "or" but in this case, it's used for emphasis or to introduce a statement.
* te: This is the object pronoun "you" in the informal "tú" form.
* lo: This is the object pronoun "it" referring to the thing being sent.
* mando: This is the verb "to send" in the future tense.