diff --git a/LDDsimulation/README.md b/LDDsimulation/README.md
index 64d108d401551d2841bff856385a36d4e14d6c63..14fad4b973d779b25963f1eb21fe5c8542724bee 100644
--- a/LDDsimulation/README.md
+++ b/LDDsimulation/README.md
@@ -57,10 +57,16 @@ Note that this method needs to be revisited if parallelisation is to be implemen
 Similarly, if more general types of gli methods need to be considered, this is where it needs to happen.
 - `calc_gl0_term(*kwrgs)`: Method that gets called by the `LDDsimulation.prepare_subdomain(*kwrgs)` within the `LDDsimulation.prepare_LDDsolver(*kwrgs)` method to calculate the initial gl0 term at the beginning of the calculation of the solution of a new timestep.
 As the normal flux gets calculated explicitly here, parts of the model are hard coded in this method aswell. Bare that in mind, when implementing new models.
-A layer of abstraction for the flux might be usefull here. 
-
+A layer of abstraction for the flux might be usefull here.
 
 ## `boundary_and_interface.py`
+This files contains two classes a general `BoundaryPart` class and a derivative of that, the `interface`
+- `BoundaryPart`: This class basically implements an `inside` method to mark marker functions on a mesh along a list of dolfin points forming a polygonal chain (which the interfaces are).
+- `interface`: interface is a subclass of `BoundaryPart` providing methods to
+deterime which dofs of an FEM function space actually lie on the interface.
+In addition, dictionaries to save and communicate gli dofs are objects of this class. In an LDD simulation, each interface holds the information which two subdomains are adjacent to it and this can be queried by the subdomain.
+
+A global list of all indices is saved as dictionary `LDDsimulation.interfase` in an instance of `LDDsimulation` and each subdomain of class `domainPatch` gets this list along with information which of these interfaces actually belong to that subdomain. 
 
 ## `solutionFile.py`
 This file defines a class `SolutionFile(dolfin.XDMFFile)` around the `dolfin`