Information:

• What is a PSD file (PSD template)?
  PSD templates are usually a layered file format used to create and edit images in Adobe Photoshop. The uniq thing is that it can save images in layers. It can be very very useful for further manipulations and adjustments with the images. PSD images can be opened with Adobe Photoshop or Photoshop Elements.
  
  What are plug-ins?
  A plug-in is a set of software elements that supplements particular potentialities to many software applications. A lot of popular applications use plug-ins, including all Adobe software, like Photoshop, After Effects, Premiere, Illustrator and others. Usually graphics software use plug-ins to support file formats and process pictures.