As said in wikipedia's page
More precisely, space can be viewed as an extremely fine fabric or network "woven" of finite loops. These networks of loops are called spin networks. The evolution of a spin network over time is called a spin foam. The predicted size of this structure is the Planck length, which is approximately 10−35 meters. According to the theory, there is no meaning to distance at scales smaller than the Planck scale. Therefore, LQG predicts that not just matter, but space itself, has an atomic structure.
Throughout the years many theories were proposed for describing what matter is made of. This effort lead to the standard model, which as far as I know is currently our better understanding about the structure of matter.
Now, as I understand, loop quantum gravity is a theory that does the same for spacetime. It proposes spacetime has an atomic structure. So I believe this is a theory trying to describe the structure of spacetime, what spacetime is made of in some sense, as has been done for matter for many years.
Interestingly, it is the first time I read about a theory that tries to do so. Is loop quantum gravity the only theory that tries to describe what spacetime is made of, or in other words, the structure of spacetime? Are there any other seriously considered theory that also deals with the structure of spacetime?
I ask "seriously considered" because obviously is a possibility that some kind of theories have already been proposed but by some reason (either theoretical or experimental) have not been considered as going in the right direction. As far as I know, although still a research topic, loop quantum gravity is somehow considered as a valid way for describing quantum gravity.