The Langlands program orginally referred to a collection of conjectures proposed by Robert Langlands over 50 years ago to connect a wide range of mathematical concepts and structures, which has been highly influentical ever since. The talk will describe some of the mathematical problems that can be solved with the help of the Langlands program, or that fit under its umbrella. Most of these problems arise in number theory, but the applications, as well as the methods involve geometry, representaion theory, and harmonic analysis; there will even be a glimpse of quantum physics. The talk will also give a scope of how the Langlands program is constantly expanding.