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.
  What is vector graphics?
  Vector graphics is the creation or modification of digital images through the use of geometrical primitives such as points, lines, curves, and shapes. Vector images are very useful for designers, because they can be scaled to any size without loss of resolution. For creating and editing vector graphics you have to use Vector graphic drawing software like Adobe Illustrator or CorelDraw.
  What is clip art?
  Clip art means any image, graphic, texture or background, photo art, stock photos art or any other image. Many of the images are can be used in publications, including newsletters, craft projects and desktop publishing projects.
  What are Icons?
  Icon is a small immage that represents an object or an application. Icons are a principal function of graphical user interfaces. The primary aim of using icons is to help users absorb and process information more effectively. Icons are a visual invitation to users to try out the recent and supreme features of your Web application. Icons should capture people's attention and forward them to the new feature. Icons make website friendly, inviting and professional.