When the temperature is same, it means that the kinetic energy of the particles of both phases are the same, so what is the difference between a vapor and liquid of a substance, such as ethanol, when they are in the same temperature?
As silly as it sounds, the difference is that one is a gas, and the other is a liquid. The vapour has the properties of a gas, i.e. it expands as much as it likes, it compresses according to certain laws, etc. The liquid has different properties. Effectively, they will look different, as you imagine a liquid and a gas being different. The gas will be a gas, the liquid a liquid.
The problem here, is that you think the phase of a substance is a function of its temperature only. This is not necessarily the case. I can heat ice up to 0 C, and it will still be ice. Conversely, I can cool water down to 0 C, and it will still be water. To have it actually go across the critical point, I have to spend some additional energy, called latent heat.
A critical point is a value of temperature (and pressure, and whatever else) where the two states of matter coexist.