Full Form of extensions that are used in different files.

Extension	Full Form
.3GP	3rd generation protocol
.AAC	Advanced audio codec
.AC3	Dolby digital sound file
.AIIF	Audio interchange file format
.AMR	Adoptive multi rate
.AWM	Adoptive multi rate wideband
.AVI	Audio video interleaved
.CDA	Compact disk audio
.DLL	Dynamic link library
.EXE	Executable format
.FLAC	Free lossless audio codec
.FLV	Flash live video
.GIF	Graphics interchange format
.JAD	Java application development
.JAR	Java archive
.MIDI	Musical instrument digital interface
.MMF	Music mobile format
.MP2	Mpeg audio layer 2
.MP3	Mpeg audio layer 3
.MP4	Mpeg layer 4
.MPGE	Motion picture experts group
.PDF	Portable document format
.PNG	Portable network/new graphics
.RM	Real media
.SIS	Symbian installation source
.SWF	Shock wave flash
.VOB	Video object
.WAV	Waveform pcm audio
.WMA	Windows media audio
.ZIP	Zone improvement plan
.TXT	Text file
.JPG	Joint photographic experts group
.PSD	Photoshop standard document