As shown in the following diagram, a Responsive Ad or what we call STRETCH™ Ad is essentially a Responsive Creative plus a format or Flowline.™
When you upload PSD files or use a Template, you are creating a Responsive Creative
Responsive Creative is a cloud-hosted completely fluid HTML5 creative with all of its elements and assets.
Format (Flowlines™) determines the shape of that fluid creative for different ad placements or slots.
Once you create a Responsive Ad or STRETCH™Ad, you can have as many different tags and deployments as you like. This is very useful if the STRETCH™Ad you create will be running in different placements and you want to track each of those placements accordingly.