Cats love to scratch almost anything.
All kinds of cats, whether big or small, have claws that retract except for cheetahs that just have semi-retractable claws because of their habit of running. Aside from using their claws to hunt, they also use these to climb trees and gain traction so when these tools are stored when not in use, they remain sharp.
However, when lions scratch a tree trunk, this does not only allow them to condition their claws but also lets them mark their territory by means of their paws' sweat glands as earlier mentioned.
Members of the feline family smell with an open mouth.
Cats have a severely strong sense of smell due to the several millions of receptors that line their teeny weeny noses (in contrast to humans that just have 5 million olfactory receptors). In addition, they are among the animals with an organ that can detect other scents. Such is called Jacobson's organ, which is located at the nasal cavity base and is present in cats as well as dogs, pigs, cattle, snakes and lizards.