[frankthetank966]

I am working on a flash ad and trying to determine what the difference between all these are.

My options are to make:
-format: SWF file:n/a
-format:GIF file:(AUTOGEN)

[Thorzdad]

SWF = Shockwave / Flash object
GIF = Graphics Interchange Format. Your basic web graphics file format. Usually lower quality than jpeg. Can include hard-edged transparency.
AUTOGEN = Not a file format. Looks like it's calling to auto-generate a GIF from some source.

[Oisín]

Flash movies are SWF files. Videos on YouTube, etc., are SWF files.

GIF is basically an image format, like JPEG, but it allows for motion in the image. Animated GIFs easily get extremely big and clunky, though. SWF is ‘optimised’ for actual video content, GIF is not.

[frankthetank966]

SWF is better quality and more common for ad's on websites I am guessing?

[Oisín]

With the same output file size, SWF will give you far better quality and animation smoothness than GIF in nearly all cases, yes.

If it’s just a banner ad that changes every three seconds and has three different images, though, GIF is a safer bet, since all browsers (even the oldest, on the oldest hardware you’d be likely to still encounter) support it, and Flash blockers that keeps all Flash content from the user are becoming increasingly popular and common.

[hedmisten]

swf is exactly what you want if you are outputting for viewing on the web. my flash 8 has a lot of files to export and publish to, but swf is the most common.