The Contour Select feature is a great addition to a number of commands to allow you to choose distinct regions of a multiple contour sketch (i.e. one with many overlapping shapes). A great application for using this is floor layouts, where in one single master sketch you may want to draw in walls, floors, window openings and desks for example.
Each "shape" in the sketch would likely be extruded to different depths but it is convenient to sketch them all in one for dimension referencing. The contour select tool is primarily available in the Extrude and Revolve Boss and Cut features. When the software feels it is needed (i.e. multiple shapes detected) the contour option appears prompting you to graphically select the shapes you wish to work in.
Once you have used the sketch once, you will find it disappears from view, but if you simply show it, or better still right click and "Add to Favourites" (new for 2013) the sketch appears in a prominent position in the Feature Tree.
All you do to reuse the sketch is simply select it and choose the desired feature. The sketch is then shared so you only have to update one to affect the others.
Give it a go!