twitter icon (AI and PNG format) with gray background

Greek , eikon, "image") is an image, picture, or representation; it is a sign or likeness that stands for an object by signifying or representing it, or by analogy, as in semiotics; in computers an icon is a symbol on the monitor used to signify a command; by extension, icon is also used, particularly in modern popular culture, in the general sense of symbol — i.e. a name, face, picture or even a person readily recognized as having some well-known significance or embodying certain qualities. See more at Wikipedia.org...

ass="thumb tright">A PNG image with an 8-bit transparency layer (top), overlayed onto a chequered background (bottom). PNG (Portable Network Graphics) is a lossless bitmap image format. PNG was created to both improve upon and replace the GIF format with an image file format that does not require a patent license to use. PNG is officially pronounced as "ping" ( in IPA), but it is often just spelled out — possibly to avoid confusion with the internet tool ping. PNG is supported by the libpng reference library, a platform independent library that contains C functions for handling PNG images. See more at Wikipedia.org...