Saber and Conocer
Unlike English, there are two ways to say "to know" in Spanish. But there's not interchangeable. Saber is used for knowledge of facts, Conocer is used for things we're familiar with, like people we've met. But to get a clearer idea, here are lots of resources for you.
Online activities from the Realidades textbook
Book 1 Ch. 9B p. 460, Book 2 Chapter 1B p. 56
Excellent grammar explanations with video
Video interviews, podcasts, and grammar explanations
Online Grammar Lessons with worksheets
Music videos to help you learn!