Does anyone know what is the mentioned element in the picture? and also what is the purpose of that (it is R2 in schematic picture)? Also there is C28 in schematic picture, what is the purpose of that?
I think Colin's comment is correct. The three devices are between the hot side of the AC line coming in (after fuse and thermistor) and ground.
The resistor at right in your photo is there to bleed off high voltage from the caps within a reasonable time after power is removed. This is so you don't shock yourself from the bare wall plug when it is unplugged.
The capacitor at left is to filter out some high frequencies that shouldn't be there, but inevitably are.
Some sort of voltage clipping device makes sense for the thing in the middle. Often you would see a TVS or MOV here. A gas discharge tube is somewhat unusual in my experience, but that does look like one, and it would serve the right function.