Add intro and move existing Intro into Getting Started

docs/source/GettingStarted.rst

+.. _Chap:GettingStarted
+
+Getting Started
+==================
+
+.. toctree::
+   :maxdepth: 1
+
+   Structure
+   BuildingCMake
+   BuildingGMake
+   RunningTestSuite
+   RegressionTesting
+

docs/source/Introduction.rst

-.. _Chap:Introduction
-
 MFiX-Exa Introduction
 ==================
 
-.. toctree::
-   :maxdepth: 1
+MFiX-Exa is a new massively parallel code for computing multiphase
+flow in which solid particles interact with the gas surrounding them.
+
+It is built on top of AMReX, a publicly available software framework designed for building
+massively parallel block-structured adaptive mesh refinement (AMR)
+applications.
+
+MFiX-Exa relies on the same fundamental physics as in MFIX but the spatial and
+time discretizations differ.  Specifically,
+
+-  Fluid velocity is defined at cell centers; pressure is defined at nodes.
+
+-  The advection algorithm includes an intermediate MAC projection for face-centered 
+    advection velocities
+
+-  Incompressibility of the fluid is imposed through the use of a projection at the
+   end of the time step rather than through SIMPLE iterations
+
+-  The representation of the complex geometry includes mesh refinement around the 
+   fluid-solid interface, which is represented used the embedded boundary, or
+   cut-cell approach
+
+-  Parallelization via flat MPI, OpenMP, hybrid MPI/OpenMP, or MPI/MPI.   
+
+-  Porting of MFiX-Exa to GPUs is in progress.
+
+-  Parallel I/O using AMReX native I/O or HDF5.
+
+-  Plotfile format supported by AmrVis, VisIt, ParaView, and yt.
 
-   Structure
-   BuildingCMake
-   BuildingGMake
-   RunningTestSuite
-   RegressionTesting
+MFiX-Exa is being developed at NETL, LBNL, and CU as part of DOE's Exascale Computing Project.
 

docs/source/index.rst

@@ -21,6 +21,7 @@ the master branch at the beginning of each month.
    :caption: Contents:
 
    Introduction
+   GettingStarted
    Particle
    ParticleBasics
    ParticleFluid