docs: add description for sobol analysis

docs/source/sensitivity/index.rst

@@ -2,11 +2,11 @@
 Sensitivity
 ***********
 
-This module hosts functionality for methods of sensitivity analysis.
+This module hosts functionality for sensitivity analysis methods.
 
 Currently implemented classes are:
 
-* :class:`.SobolAnalyze`:
+* :class:`.SobolAnalyze`: Compute Sobol' sensitivity indices.
 
 .. toctree::
    :maxdepth: 1

docs/source/sensitivity/sobol.rst

-Sobol' Sensitivity Analyze
-==========================
+Sobol' Sensitivity Analysis
+===========================
+
+This module is used to compute Sobol' indices given model (e.g. simulator or emulator)
+outputs evaluated at chosen Saltelli samples (see the :class:`.Saltelli` class).
+Detailed description of the theory can be found in :cite:t:`Saltelli2002` and :cite:t:`Saltelli2010`.
+The :class:`.SobolAnalyze` class relies on the Python package `SALib` :cite:p:`Herman2017`.
 
 SobolAnalyze Class
 ------------------