Datasheets
L298N, HC-06 and ATmega328P datasheets
The real documents: manufacturer datasheets for the parts in the car, as the manufacturers published them. Nearly every disagreement online about these parts is settled by one of these PDFs. Where a datasheet describes the bare chip and you are holding a module, the explained page covers the difference.
HC-06 Bluetooth serial module
Guangzhou HC Information Technology · Module data sheet Rev 2.2 · 2011-04 · 17 pagesThe Bluetooth serial module in the car. The datasheet covers the bare 34-pad module; the explained page maps it onto the 4-pin breakout board and lays out the AT commands.
L298 dual full-bridge driver (L298N)
STMicroelectronics · DS0218 Rev 5 · 2023-10 · 23 pagesThe dual H-bridge on the red motor-driver module. The datasheet covers the bare chip; the explained page pulls out the numbers that matter and maps the chip's pins onto the module.
ATmega328P
Microchip · DS40002061A · 25 pagesThe microcontroller on an Arduino Uno. This is where the input-threshold number comes from: a pin reads HIGH above 0.6 × VCC, which is 3.0V on a 5V board, and that is why a 3.3V module can drive the Arduino directly.
These are the manufacturers' own documents, republished so the books and these pages can point at something stable. Copyright remains with the respective manufacturers.