Thank you for your kind answer, I've found a detailed photo of what I wanted to buy, it has micocontroller, probably to manage the relay depending what coming from wifi, so I suppose I can't manage directly wifi by Arduino. I wanted ask infos about this board because there is one in the next shop, and I don't need to order it from China.The mistery is why it has TX and RX, what for? Maybe to program the local microcontroller? ProbablyYes the model you suggested has the 5/3.3 adaptor..
Thank you again for answer..there is RX TX pin on board, but also a microcontroller, probably used to manage time and activation of relay. In my opinion these TX RX goes to it for programming it, and not to WiFi module. Only who bought it already can know that.. this is why I asked here.I give very low probability that RX TX goes to Wi Fi and I can use it as the module without microcontroller