This week in my ninth grade computer science principles class we started talking about big data and algorithms. One of the resources that I used in introducing this topic was Common Craft's explanation of algorithms. The two and a half minute video explains what an algorithm is and the roles that algorithms can play in our lives, particularly in our online lives.
After they watched the video I had my students list some other ways they could think of that algorithms are or could be used in their lives. The most common example in my classroom was in the videos that are suggested to them on YouTube.
Disclosure: I have a long-standing in-kind relationship with Common Craft.