When you're walking on the perfect green grass of a golf course, you might remark on the gorgeous turf. Turf is the top layer of ground, especially when it's planted with grass.
From its original meaning, referring to the top layer of soil in which plants are rooted, turf has expanded to include a range of senses. While you might carefully maintain your beautiful backyard turf, your dog might think of it as his turf, barking to defend it from intruders. This sense of turf means "range of influence," or territory. Both meanings of the word come from a Germanic root that originated in a Sanskrit word, darbha, "blade of grass."