Braverman, Finkelberg and Nakajima have recently given a mathematical construction of the Coulomb branches of a large class of 3d N=4 gauge theories, as algebraic varieties over the complex numbers with Poisson structure. Quiver gauge theories form a particularly interesting class of theories, with several mathematical connections to geometric representation theory. vIn this talk I will overview some known properties of the Coulomb branches of quiver gauge theories, following the BFN definition. I will also outline a proof that they have symplectic singularities, which in particular implies that these Coulomb branches have finitely many (holomorphic) symplectic leaves.