The ESP32 chip is an MCU with Wi-Fi and Bluetooth network modules. This chip is developed by Espressif. For further information about the ESP32 chip, I recommend that you read the product documentation at http://espressif.com/en/products/hardware/esp32/overview.
There are a lot of boards based on ESP32. You can find various boards based on ESP32 from SparkFun, Adafruit, or embedded companies from China. To work with AWS IoT on the ESP32 chip, we can apply the Mongoose OS platform from Cesanta. You can review the details of this platform on the official website at https://mongoose-os.com.