Our friends at SpeedoInternational made a video about swimming the stroke we're learning. The swimmer you see has good technique, because he's learned and practiced for many years. See how he rotates to breathe? Where do his eyes look when he swims?
When people first began to swim like this, they called it Front Crawl. This name is still used today, but most now call it Freestyle.
Like many skills we perform, they improve over time. The folks at British Pathé put together this video showing the changes that have happened to the Freestyle stroke.