When we walk out with our camera and select a part of the world to make an image from we are choosing detail. This bit seems to say what we are visualizing better than that over there, and our viewfinder zeros in for the snap. This might be a snapshot with our smart phone, unplanned and quickly chosen, or a carefully set up studio shot, or a landscape chosen for its specific lighting and point of view. In a way we are being hunter gatherers at this point, selecting and harvesting, and that ultimately might be the attraction of photography. Think about photo-safaris.
The confusion about detail is if we think of our viewfinder as the 'frame'. At the moment of capture, as we press the shutter, it is simply a gun-sight, and we then drag our game home to the fireside. Once within the computer our digital image is like the story of the hunt: within the limits of the information/details captured we can choose how we tell the story, how we organize as we crop and otherwise adjust our image. Everything within the edges of the frame is in relationship, so the detailed visual information we find there is all contained within the original capture. The snow bank that fills the screen with its soft gradations of tone is set off, defined, by a thin triangle that shows the top of the snow and an orchard tree in the distance: That is there to define form, its job is simply to animate that other detail, the snow.
I peer down from the wharf and see green water and a single red leaf and take a photograph. The detail encompasses the whole shallows , the supports of the dock and that leaf off in one corner. Later, within the final frame, the green interacts with that one spot of red, but the leaf is not the 'detail' but a part of the final image that expresses that red/green relationship.
I seem to be splitting hairs, defining detail so narrowly, detail being a selected part of reality and frame being about relationship, and we know that in reality we take a photograph with detail and frame and shutter speed and camera angle and aperture all present as we press the shutter. So, this is a way of understanding that in photography, as opposed to other visual arts, we work with what is before us, the things of this world, and that we need to select carefully if we are to express accurately. The detail we hunt for or dig from the productive soil of our imagination is all important.