diff --git a/docs/source/simulator/run_simulator.rst b/docs/source/simulator/run_simulator.rst
index 95efe48da91e42341b627d043c57c463c8f838ea..5a24b32af9a193e35ee1bddbeb60e8a74995be4f 100644
--- a/docs/source/simulator/run_simulator.rst
+++ b/docs/source/simulator/run_simulator.rst
@@ -1,6 +1,17 @@
 Run Simulator
 =============
 
+A `simulator` which describes certain real-world system is often subject to
+uncertainties. Uncertainty-related analyses require running the `simulator`
+multiple times at different variable input points. Class :class:`.RunSimulator`
+implemented in this module provides functionality to sequentially or parallelly
+execute `simulator` at a number of varaible input points.
+
+The user needs to define their `simulator`, implement an interface (essentially
+a Python function) to call the `simulator` from within Python and return output
+of interest, and inform :class:`.RunSimulator` the signature of the interface.
+
+
 RunSimulator Class
 ------------------