It was 1995 when NAMD was introduced (Nelson et al.) as a parallel molecular dynamics code enabling interactive simulation by linking to the visualization code VMD. In 1999 a major improvement was accomplished in NAMD 2 (Kalé et al.), scaling to 200 processors at the time due to the efforts and software of the Parallel Programming Lab. NAMD has since matured, adding many features and scaling to thousands of processors, garnering accolades and users in the process. This progress is now collected in a NAMD review paper that presents, in a manner accessible to the novice researcher, the concepts and algorithms behind NAMD, features for steered and interactive MD and for free energy calculation, the elements of the NAMD design that enable parallel scaling, performance comparisons of a variety of platforms, and advice for productive use of NAMD on modern research projects. Case studies ranging from the typical to the elaborate demonstrate the capabilities and flexibility of NAMD. This new reference provides an excellent foundation for working through the extensive NAMD tutorials, either on your own or at a hands-on workshop.