A field theory admits different types of symmetries, with the two most common ones being global and local symmetries. Global symmetries are fields transformations acting the same way everywhere while local symmetries act on fields in a position dependent way. The latter correspond to redundancies in the description of the system. This is a consequence of Noether's second theorem which states that each local symmetry degree of freedom corresponds to a relation among the Euler–Lagrange equations, making the system underdetermined. Underdeterminacy requires gauge fixing of the non-propagating degrees of freedom so that the equations of motion admit a unique solution.