On Windows versions of After Effects, AVI appears listed with the more comprehensive name, "Video for Windows". In fact, it's the format specified by the default Output Module template. The Format Options button will reveal the AVI/VfW codecs available on your system.
On Mac systems, AVI/Video for Windows is not available as a direct export option (except through the File > Export path, which is really not recommended). Export a lossless intermediate file from the Render Queue instead (for example, a Quicktime file). You can then use a number of converter applications (including Quicktime Pro, for example) to convert this intermediate file to an AVI file.
Seriously? Use a file converter if you're on Mac? You making a professional software and I pay for if (not so cheap). But for simple operation I must pay someone else. Quictime pro is no longer available. AVI is not something weird, it's one of standards and should be everywhere. I have no words
How is this still the only answer I can find about this in 2022? This answer is over 10 years old and it seems to still be the only available solution for exporting .AVI on a Mac. Completely ridiculous adobe.