This lecture focuses on exploring Thymio's proximity sensors, essential for its navigation and obstacle avoidance capabilities. Thymio is equipped with 7 horizontal sensors, 5 in the front and 2 in the back, along with 2 ground sensors. The instructor demonstrates how to program Thymio to move, stop in front of obstacles, navigate with walls, and follow a black line on the ground, culminating in integrating these behaviors into a single program.