What extensions mean.
WHAT AN EXTENSION IS
The part of a filename after the final dot, indicating what kind of file it is.
WHY IT MATTERS
It determines which program opens the file.
COMMON DOCUMENT TYPES
Word processing documents Spreadsheets Presentations Portable documents, which preserve appearance everywhere Plain text
COMMON IMAGE TYPES
Photographs, compressed Graphics with transparency Vector graphics, which scale without loss
COMMON OTHER TYPES
Compressed archives Audio and video Databases
WHAT TO DO WHEN A FILE WILL NOT OPEN
Establish its type, and whether you have software that opens it.
WHAT TO BE CAREFUL WITH
Files whose extension does not match their content Executable files received from others Documents asking to enable content
THAT LAST ONE
A document asking to enable content is asking to run code.
WHAT TO ENABLE ON YOUR MACHINE
Display of file extensions.
WHY
So you can see what a file actually is.
