Reference to your website in this article only applies if you have your website provided by Eagle.
Property listing images on your website/brochures are generally displayed with a 4:3 aspect ratio, where for every 4 pixels of width, there is 3 pixels of height. Some example resolutions of this aspect ratio are 1200 x 900 or 2000 x 1500.
To avoid having white space either top/bottom and left/right sides of the image, your website/brochure will fit the image to the space.
This is occurring because the website/brochure has fixed dimensions so it will hold that space accordingly.
So if the image is too wide, it will hold the height and crop the left and right edges.
If the image is too tall, it will hold the width and crop the top and bottom edges.