1008p is a high definition TV video mode standard used by Blu-ray discs containing 1080 horizontal lines of resolution and a progressive scan (i.e. the image is not interlaced).
A 1080p transfer typically has a 16:9 ratio, giving an image resolution of 1920 x 1080 pixels.
Films that a ratio differing from 16:9 will typically have black matte areas added to the image.
In the case of North by Northwest, the Blu-ray release uses the entire image frame and there are no black matte areas:
For older films, shot in 1.37:1 ratio (also known as "Academy ratio"), black matte areas (highlighted in red in the second example) are added to either side of the image to create a 16:9 image:
If the image frame is wider than 16:9, black matte bars are added to the top and bottom of the image: