Hi Zuzana,
thanks for stepping in. Greatly appreciated!
So that means we are right about the rest? 
What I don’t understand about your definition is why it is necessary to project a 3D Tie Point? And what is the purpose of that projection? And just to split hairs, nobody mentioned pairs of images… 
I never think of it that way even though I understand that pairs are somehow relevant in some stage (depth map creation)?
The way I understand it is that an image has features on a 2D plane. This plane has a “beamer” behind it that projects those 2D features out into space along a line. Where those (of the same Tie point on different images with different beamers) intersect, a Tie Point is born. Or are there different levels of Tie Points? A 2D kind on the images and also the results in 3D? Because in terms of nomenclature, Tie Point indicates 2D, as in tying different images together. At least thats how I interpret it logically, which is not always a good idea with technical terms…
A quick search in my favorite search engine confirmed it to be the 2D point in an image. So how are the 3D points to be adressed properly? Just Points? 3D Tie Points?