This is the first part of a series talk on symplectic duality. Symplectic duality is a duality between a pair of symplectic resolutions where a measurement on one resolution matches with another measurement on its dual resolution. We first introduce the notion of symplectic resolution and explain how it naturally arises from the study of Coulomb/Higgs branches of 3D N=4 gauge theory, leading to the understanding of symplectic duality as 3D mirror symmetry in physics. After covering those generalities, we restrict our concern to quiver gauge theory and give explicit descriptions of both of the branches. Throughout, the Springer resolution and resolution of Kleinian singularity will serve as our running examples.