Some host servers may not be setup to handle specific file types such as mp3 or swf files. Using htaccess can fix this oversight. This oversight may actually be on purpose though, so check with the host administrator before doing this.
AddType specified you are adding a new mime type (file type). application/x-shockwave-flash is the actual mime parameter specs. swf is the extension of the file type.
In the above example, we are showing how to add an SWF file which is a Shock Wave Flash file.