you can think of spaces in OpenGL as local coordinate-systems
i.e. if we both stand on a 100m race track, me at 50m and you at 70m.
YOu are now standing +20m to my relativ space.
So in computer graphics we usualy have 4 spaces:
- object/local/model space, relative to the object - your model files are all in this space
- world/global space the coordinate system of your game
- camera/view/eye space relative to your camera - let you know if a object is i.e. 1m far of your face
- screen space on which screen pixel a object is located
one always use a matrix to convert from one space to another, to get the other direction one can use the invers of that matrix