All files are tar archives, compressed with gzip. After downloading, you will have to gunzip and unpack the archive. Then, follow the instructions in the file README.
Each MeatAxe package has a version number composed of major version, minor version, and patch level. Major versions are incremented when there are changes that are not backward compatible. Minor version number increments indicate added features or changes that are still backward compatible. Released versions are not changed, but bugfixes may be applied, leading to an incremented patch level.