.7z = 7zip compression
Like lha, zip, rar and all the rest. Seems to compress better than most though.
7z is the new archive format, providing high compression ratio.
The main features of 7z format:
- Open architecture
- High compression ratio
- Strong AES-256 encryption
- Ability of using any compression, conversion or encryption method
- Supporting files with sizes up to 16000000000 GB
- Unicode file names
- Solid compressing
- Archive headers compressing