Loop quantum gravity (LQG) is a theoretical framework aiming to describe quantum spacetime. It has evolved over the past 25 years, with initial ideas emerging from a 1986 workshop and first conference talks in 1987. The theory has generated significant interest, faced opposition, and now is developed by around forty research groups globally. The paper provides a critical assessment of LQG's progress, successes, and limitations. LQG is based on a discrete, quantum description of space, where space is composed of "quanta" or "grains" of space. These quanta are represented by spin networks, which are graphs with nodes and links, where nodes represent quantum of space and links represent connections between them. The theory is Lorentz invariant and can be coupled to fermions and Yang-Mills fields, as well as a cosmological constant. The theory's quantum geometry is defined by the spin-geometry theorem, which relates the algebra of momentum operators to the existence of a metric. The spin network basis diagonalizes area and volume operators, providing a discrete, quantum description of spacetime. The theory's transition amplitudes are defined by integrals over two-complexes, which are analogous to Feynman diagrams in quantum field theory. LQG addresses the problem of whether there exists a consistent quantum field theory whose classical limit is general relativity. It aims to resolve the lack of predictivity in current theories at high energies and provides a discrete, quantum description of spacetime. The theory has been shown to have ultraviolet finiteness, as the area gap is discrete and the theory avoids ultraviolet divergences. LQG is not a theory of unification, but rather a theory of quantum gravity. It does not address the unification of all forces, but instead focuses on the quantum nature of spacetime. The theory has been derived from classical general relativity through various methods, including the Wheeler-deWitt equation and the use of Ashtekar variables. The theory has faced challenges, including the need to understand the action of the Hamiltonian constraint on nodes and the physical implications of the "loopy" geometry. However, the spin network basis has provided a solution to these problems, with spin networks representing quantum states of space. The theory has also been shown to have a discrete, quantum description of spacetime, with the area and volume operators being diagonal in the spin network basis. In conclusion, LQG is a promising approach to quantum gravity, providing a discrete, quantum description of spacetime and addressing the problem of whether there exists a consistent quantum field theory whose classical limit is general relativity. The theory has made significant progress in the past 25 years, but still faces challenges in fully understanding its implications and verifying its predictions.Loop quantum gravity (LQG) is a theoretical framework aiming to describe quantum spacetime. It has evolved over the past 25 years, with initial ideas emerging from a 1986 workshop and first conference talks in 1987. The theory has generated significant interest, faced opposition, and now is developed by around forty research groups globally. The paper provides a critical assessment of LQG's progress, successes, and limitations. LQG is based on a discrete, quantum description of space, where space is composed of "quanta" or "grains" of space. These quanta are represented by spin networks, which are graphs with nodes and links, where nodes represent quantum of space and links represent connections between them. The theory is Lorentz invariant and can be coupled to fermions and Yang-Mills fields, as well as a cosmological constant. The theory's quantum geometry is defined by the spin-geometry theorem, which relates the algebra of momentum operators to the existence of a metric. The spin network basis diagonalizes area and volume operators, providing a discrete, quantum description of spacetime. The theory's transition amplitudes are defined by integrals over two-complexes, which are analogous to Feynman diagrams in quantum field theory. LQG addresses the problem of whether there exists a consistent quantum field theory whose classical limit is general relativity. It aims to resolve the lack of predictivity in current theories at high energies and provides a discrete, quantum description of spacetime. The theory has been shown to have ultraviolet finiteness, as the area gap is discrete and the theory avoids ultraviolet divergences. LQG is not a theory of unification, but rather a theory of quantum gravity. It does not address the unification of all forces, but instead focuses on the quantum nature of spacetime. The theory has been derived from classical general relativity through various methods, including the Wheeler-deWitt equation and the use of Ashtekar variables. The theory has faced challenges, including the need to understand the action of the Hamiltonian constraint on nodes and the physical implications of the "loopy" geometry. However, the spin network basis has provided a solution to these problems, with spin networks representing quantum states of space. The theory has also been shown to have a discrete, quantum description of spacetime, with the area and volume operators being diagonal in the spin network basis. In conclusion, LQG is a promising approach to quantum gravity, providing a discrete, quantum description of spacetime and addressing the problem of whether there exists a consistent quantum field theory whose classical limit is general relativity. The theory has made significant progress in the past 25 years, but still faces challenges in fully understanding its implications and verifying its predictions.