If you have an Arduino, you may have run into a project that required the board to make sounds. One of the cheapest and easiest ways to accomplish this is to use a Piezo Buzzer.
Piezo Buzzers are extremely simple to wire, and have very simple code.
This video explains how a Piezo Buzzer works, how to use it, and how to wire/code it.
If you have any questions, leave one here or on the video and I'll get to you as soon as I can. Enjoy!