It is really supposed to be a harmless non physical fling.
I notice someone gazing at me from across the room. My friend calmly reminds me that I am in the Netherlands now.
I gaze back and he gives me a crack of a smile that has some hidden truth. Once he expresses his interest (by eyeballing you it seems) you are usually supposed to go to him and talk to him and that seals the deal. A Dutch person would have gotten the flirtatious cue.
I have no qualifications in the field but I find it interesting to go around analyzing human behaviour (not in an intrusive way) to amuse myself. Please do not get me wrong, I am not a stalker nor do I have sociopathic or psychopathic tendencies, I just find the human species an interesting, complicated and weird lot.
Take note that the following is solely based on my experience and experiences of those associated with me.
I am used to someone coming over and talking to you (chatting you up, as the British would say), perhaps offering a drink and getting to know you a little better before it is a done deal.