If your introduction to digital electronics came more years ago than you’d care to mention, the chances are you did so with 5V TTL logic. Above 2V but usually pretty close to 5V is a logic 1 ...
He’s wondering if the ESP8266 is 5V tolerant after all. If it is, great. We don’t need level converters, and interfacing the ESP to USB TTL serial adapters becomes much easier. Yes ...