[en] This is a tutorial overview of the PARMILA drift-tube linac beam-dynamics code. First discussed are what PARMILA is and what it is used for. Its origins are discussed. What PARMILA does and how it does its tasks are described. One of the major uses of PARMILA is for the evaluation of effects produced by errors in construction and deviations from design operating conditions. In this connection, a few words are said about what errors PARMILA is able to handle. A section on user friendliness is followed by a few words on the code's accuracy. Finally, some options and improvements are proposed