Raster or bitmap, is a different kind of rendering style on how an image can be put on a screen using pixels. Raster images lose their aspect ratio the more it is increased in size, as pixels are not scaling points, they are forced to grow as well (stepping) as you do not get new pixels.

Vector - an angle based on at least 2 points alluding to points in space relative to each other that you can use to create shapes based on their relationship, defined by the angles. Vector images maintain their aspect ratios and will not lose quality, however you are limited e.g. photogenic pictures such as the artwork for posters and shop POS for games like GTA V and Call of Duty: Ghosts

Aspect ratio definition:

The ratio of the width to the height of the image on a television/computer screen


Resolutions that conform to a 16:9 aspect ratio


480 x 234

480 x 272

640 x 360

848 x 480

854 x 680

960 x 540

1136 x 640

1280 x 720

1366 x 768

1600 x 900

There are many more that go into super HD formats for example 4320p which is used for Ultra high definition television for example 85-Inch Direct-View LCD TV http://www.youtube.com/watch?v=9U7e_quvkPQ