When you open PowerPoint 2013, rather than getting a blank document, like you did in previous versions of PowerPoint, you get the Start Screen. Here you can open recent presentations or start from scratch with a lovingly prepared template.
Templates can be pinned to the Start Screen as shown below.
For topic specific templates use the Suggested searches the top, or use the Search bar.
You can always get back to the Start Screen by clicking on the File tab on the Ribbon and clicking New in the menu.
Disable the Start Screen on Startup
If you find the Start Screen a bit annoying – (I understand), you can disable it. Click on the File tab on the Ribbon and select Options at the bottom of the menu.
Make sure the General section is selected, top left of the Options dialog (it is by default) and then under Startup options untick Show the Start screen when this application start.