AFF4 Segments are seekable units of data which are stored in a single unit. When a segment is loaded, the entire segment exists in memory at the same time. For this reason the segment size should be limited and not very large.
The ZipFileSegment is a special kind of segment which is stored in an AFF4 ZipFile volume. It is stored in a single archive member and may be compressed inside the archive using the zlib deflate compression.