The Born-Oppenheimer molecular potential energy surface (PES) is central to how chemists think about the structure and dynamics of molecular systems, ranging from equilibrium structures at minima to product-channel asymptotes, connected by paths across landscapes and over energetic barriers. In this framework, the potential for the nuclei is obtained by connecting electronic energies at a series of discrete nuclear positions (geometries) into a surface. PESs are the essential starting point for nearly all calculations of quantum states, properties, and dynamics of molecules making them the foundation of theoretical chemistry.