Addressing PR comments.

Author: Rogan Carr

docs/samples/Microsoft.ML.Samples/Dynamic/Transforms/SelectColumns.cs

@@ -42,19 +42,19 @@ public static void Example()
             var rowEnumerable = mlContext.CreateEnumerable<SampleInfertDataTransformed>(transformedData, reuseRowObject: false);
 
             // And finally, we can write out the rows of the dataset, looking at the columns of interest.
-            Console.WriteLine($"Label and Educations columns obtained post-transformation.");
+            Console.WriteLine($"Age and Educations columns obtained post-transformation.");
             foreach (var row in rowEnumerable)
             {
-                Console.WriteLine($"Label: {row.Age} Education: {row.Education}");
+                Console.WriteLine($"Age: {row.Age} Education: {row.Education}");
             }
 
             // Expected output:
-            //  Label and Education columns obtained post-transformation.
-            //  Label: 26 Education: 0 - 5yrs
-            //  Label: 42 Education: 0 - 5yrs
-            //  Label: 39 Education: 0 - 5yrs
-            //  Label: 34 Education: 0 - 5yrs
-            //  Label: 35 Education: 6 - 11yrs
+            //  Age and Education columns obtained post-transformation.
+            //  Age: 26 Education: 0 - 5yrs
+            //  Age: 42 Education: 0 - 5yrs
+            //  Age: 39 Education: 0 - 5yrs
+            //  Age: 34 Education: 0 - 5yrs
+            //  Age: 35 Education: 6 - 11yrs
         }
 
         private class SampleInfertDataTransformed

src/Microsoft.ML.Data/Transforms/ExtensionsCatalog.cs

@@ -75,10 +75,10 @@ public static ColumnSelectingEstimator DropColumns(this TransformsCatalog catalo
         /// <remarks>
         /// <format type="text/markdown">
         /// <see cref="SelectColumns"/> operates on the schema of an input IDataView,
-        /// either dropping unselected columns from the schema or keeping them but hiding them from the user. Keeping columns hidden
+        /// either dropping unselected columns from the schema or keeping them but marking them as hidden in the schema. Keeping columns hidden
         /// is recommended when it is necessary to understand how the inputs of a pipeline map to outputs of the pipeline. This feature
-        /// is used, for example, in saving models so that the model can be easily debugged at a later time. For more information,
-        /// please refer to [IDataView Design Principles](~/../docs/samples/docs/code/IDataViewDesignPrinciples.md).
+        /// is useful, for example, in debugging a pipeline of transforms by allowing you to print out results from the middle of the pipeline.
+        /// For more information on hidden columns, please refer to [IDataView Design Principles](~/../docs/samples/docs/code/IDataViewDesignPrinciples.md).
         /// </format>
         /// </remarks>
         /// <param name="catalog">The transform's catalog.</param>
@@ -87,7 +87,7 @@ public static ColumnSelectingEstimator DropColumns(this TransformsCatalog catalo
         /// <example>
         /// <format type="text/markdown">
         /// <![CDATA[
-        /// [!code-csharp[Concat](~/../docs/samples/docs/samples/Microsoft.ML.Samples/Dynamic/Transforms/SelectColumns.cs)]
+        /// [!code-csharp[SelectColumns](~/../docs/samples/docs/samples/Microsoft.ML.Samples/Dynamic/Transforms/SelectColumns.cs)]
         /// ]]>
         /// </format>
         /// </example>