A sight line is a way to draw the eye, from, say, your front hallway out into the garden space beyond the house, using clever lighting.
Uplight a path or a few feature plants in the garden and connect them so they come on with the hallway lights. This will create a feeling of extra space if you are showing your home in the evening. It will also make the garden feel more interconnected with the house itself.
The garden is another room in the house and must be treated as such. It may be a room that is rarely used but that's not the point. You must be able to see it from the property and know that it there the option to use it. The faint possibility of spending long, balmy evenings sipping white wine on the patio is what you are offering.
