The Edit Sketch (or Sketch, as we will usually refer to it) is a companion to every line feature or polygon feature (or feature to be created) in a geodatabase feature class or shapefile.14
When you want to create a feature with the Editor, you create a sketch. Once you save your edits, the sketch becomes a feature. If you are modifying an existing feature, when you make it a target of editing, it is the sketch of the feature that you are editing. Not until you stop editing the sketch do the modifications take effect on the feature.