Automation for my new apartment

[drazvan2003]

i saw in one of the videos - https://youtu.be/nFu80X-f-XY?si=e7pyXjuc3_DDjcLu&t=218 that there is a small pcb board that needs to be attached to the light switch. From what i understand this converts the light switch into a smart one that sends signal to the server and the server will trigger the relay to perform the action. Is that correct ? And where can i find to buy that pcb ?