- * They are generated from simgrid::s4u::this_actor::exec_init() or simgrid::s4u::Host::execute(),
- * and can be used to model pools of threads or similar mechanisms.
+ * @beginrst
+ * Most of them are created with :cpp:func:`simgrid::s4u::this_actor::exec_init()` or
+ * :cpp:func:`simgrid::s4u::Host::execute()`, and represent a classical (sequential) execution. This can be used to
+ * simulate some computation occurring in another thread when the calling actor is not blocked during the execution.
+ *
+ * You can also use :cpp:func:`simgrid::s4u::this_actor::parallel_execute()` to create *parallel* executions. These
+ * objects represent distributed computations involving computations on several hosts and communications between them.
+ * Such objects can for example represent a matrix multiplication done with ScaLAPACK on a real system. Once created,
+ * parallel Exec are very similar to the sequential ones. The only difference is that you cannot migrate them, and their
+ * remaining amount of work can only be defined as a ratio. See the doc of :cpp:func:`simgrid::s4u::Exec::get_remaining`
+ * and :cpp:func:`simgrid::s4u::Exec::get_remaining_ratio` for more info.
+ * @endrst