The remainder of this section outlines the SAPT formalism (Section 1.1), including definitions for its energy components, and modifications forming the basis of XSAPT are discussed in Section 1.2. The presentation is intended to be only moderately technical, presented as an overview but with enough detail so that a potential user can make informed choices with regard to the particular setup of an XSAPT calculation. Shorter and even less technical discussions of XSAPT can be found elsewhere. The accuracy and performance of XSAPT are discussed in Section 2. Accuracy is assessed (in Section 2.1) by comparing to benchmark ab initio results for standard noncovalent data sets, where interaction energies are available at the CCSD(T) level extrapolated to the complete basis-set (CBS) limit. Performance benchmarks for XSAPT (Section 2.2) are based on a newly rewritten version of the code that exists within the Q-Chem software package, featuring improved single-node parallel efficiency that is documented here for the first time. Finally, illustrative applications are presented in Section 3. After making some elementary remarks about the distinction between electrostatics and Pauli repulsion, and the failure of multipole ideas at nonbonded close-contact distances (Section 3.1), we demonstrate that (X)SAPT provides a much cleaner definition of dispersion as compared to DFT-based EDA schemes (Section 3.2). We then describe how XSAPT calculations have been used to upend the conventional understanding of π-π interactions (Section 3.3), and to reinforce the conventional idea that CT plays an important role ion hydrogen bonding (Section 3.4).