Update Explorer.md (#292)

docs/Configuration/Explorer.md

@@ -57,6 +57,31 @@ and
 https://localhost/Explorer/files
 ```
 
+### Charts
+The charts section configures data visualizations for the explorer page. Each chart is defined by its `chartType` and `title`.
+
+```json    
+"charts": {
+      "race": {
+        "chartType": "fullPie",
+        "title": "Race"
+      },
+      "ethnicity": {
+        "chartType": "horizontalStacked",
+        "title": "Ethnicity"
+      },
+      "gender": {
+        "chartType": "bar",
+        "title": "Gender"
+      }
+    }
+```
+
+The currently supported chart types are:
+* `bar`: a regular vertical bar chart.
+* `horizontalStacked`: horizontal stacked bar chart.
+* `fullPie`: full pie chart.
+* `donut`: pie chart with a hole.
 
 ### Download Table Data