About the MAFF file format
MAFF, compared to other web archive formats like MHTML and single-page HTML, is particularly suited to package video and audio together with related web resources. This ability derives from the basic structure of the ZIP container, where compression can be used for web pages, and verbatim storage for content that requires fast streaming access and wouldn't benefit from being re-compressed, like most video and audio.
About the Mozilla Archive Format add-on
MAFF files can be opened using any ZIP extraction utility, and most operating systems can recognize them natively after changing the file extension from .maff to .zip. Full browser integration, however, is only available in Firefox and SeaMonkey after installing the Mozilla Archive Format add-on, which can handle both MAFF and MHTML files.
Basic usage, how to convert saved pages, and more.