In this lesson, we will explore the concept of libraries in Arduino programming. We'll cover three methods for installing libraries: directly from the IDE's repository, from the IDE using a downloaded ZIP file, and by manually downloading and installing a ZIP file. Following this, we will explain the DHT11 temperature and humidity sensor in detail. We'll then proceed to install the necessary library, explain the code for the DHT11, and demonstrate its use by measuring temperature. In the second section of this lesson, we will learn how to implement an action based on temperature readings, specifically by turning on a buzzer when the temperature reaches 45 degrees.