Bit Depth

Bit depth, also known as colour depth and BPP (bits per pixel). Is a computer graphics term which describes the number bits used to make up a single pixel in a bit-map

Vector Graphics

Vector graphics is the use of geometrical primitives such as points, lines, curves, and polygons, which are all based upon mathematical equations to represent images in computer graphics.
This is a vector graphic.

A vector graphic is made up of points in space called vectors. The advantage of vector graphics, in comparison to bitmaps, is that it [...]

Pixels

A pixel, meaning picture element, is a point in a picture comprised of one colour. Pictures are made up of thousands, sometimes millions, of pixels. When these pixels are put together they appear to be connected and make a picture. Depending on the amount of pixels and the quality of the display system the resolution [...]

Raster images

A raster image (a bitmap) is a representation of pixels put together to make an image. Raster images are stored in image files with various formats.
This is a raster image

Each pixel has an individually defined colour. For instance, a typical JPEG image often consists of colored pixels defined by three bytes — one byte each for red, [...]

Graphic File Formats

These posts are about graphic file formats. Different formats are used for different files. Eg, .psd formats are used for photoshop and .fla are used for flash files. Images on the Internet are usually JPEG this is the most commonly used used file format.

*.JPEG

Joint Photographic Expert Group can be high or low quality depending on the chosen settings. Since the file size is variable, it is a commonly used file format on the internet.
This is a JPEG image.
 http://ipac.jpl.nasa.gov/media_images/ssc2006-17b1_small.jpg