This is handled in many ways.
There are administrative "switches" under Admin->Configuration-> ..... a) Layout Settings, b) Product Info, c) Product Listing, etc.
There are language files controlling text content
There are template files controlling the display of the information.
Click here for Information on the templating system and how to customize things to your liking.
For more specific questions, please go to the support forum and post a new topic in the appropriate category, with as much detail as possible about what you're wanting to do, including a URL if possible.