The <literal>[Unit]</literal> section contains generic information about the service, like its description and manual page resources, as well as relations (dependency and order) to other services. The <literal>[Service]</literal> part contains the declarations related to the service execution (starting, stopping, killing, restarting), directories and configuration file(s) used. The last section, <literal>[Install]</literal>, again carries generic information into which targets to install the service and, in this case, the alias that can be used instead of the service name. As you can see, there is very little code in there, only declarations. Systemd takes care of displaying progress reports, keeping track of the processes, and even restarting them when needed. The syntax of these files is fully described in several manual pages (e.g. <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, etc.).