updated doc for default context processors in Guides section

doc/docs/guides/context_processors.md

@@ -1,7 +1,14 @@
-## Default context Processors
+## Default context processors
 
-### settings
-all settings are copied into the context of the template
+Context processors are part of the Django template language. The context processor is applied *after* the context for a given request. In Opal we use this to give all templates access to some generic information about the internals of Opal applications.
 
-## models
-all subrecords are copied into the context of the template under the namespace models, e.g. the allergies subrecord can be referred to by models.Allergy
+### Settings
+All Opal settings are copied into the context of the template.
+
+### Models
+All [subrecords](../reference/subrecords/) (the underlying clinical models of Opal) are copied into the context of the template under the namespace `models`, e.g. the Allergies subrecord can be referred to by `models.Allergy`
+
+### Pathways
+Pathways are copied in to the context of the template under the namespace `pathways`. For an example Pathway you would be able to access attributes of a Pathway thus: `pathways.MyPathway.get_display_name`
+
+It is important to note that since the context processor is applied *after* the request context, this can lead to the context processor over-writing elements of context data. For further information on this see the Django documentation.