Coming from an Uno, three things change at once: there are two cores instead of one, the logic is 3.3 V instead of 5 V, and there is a radio on board. The radio is the reason people switch; the 3.3 V is the reason their first sensor reads garbage.

Two cores, and what runs where

The Wi-Fi and Bluetooth stacks are real software and they need CPU time. On a single-core board a network call stalls your control loop. Here the radio work sits on one core and your loop() on the other, so a slow HTTP request stops being everyone's problem.

3.3 V, and the sensor that lies to you

A 5 V sensor connected straight to an ESP32 pin may appear to work and quietly damage the input over weeks. Check the operating voltage of every part before wiring, or use a level shifter.

The Lab emulates the ESP32 including its network stack, so everything in this course runs in the browser first.