Complex sentence: Just like gzip and bzip, xz and lzma can only compress single files (or data streams) as input; they cannot bundle multiple files into a single archive; to do this an archiving program is used first, such as tar.
Split into simpler sentences: Just like gzip and bzip, xz and lzma can only compress single files (or data streams) as input. They cannot bundle multiple files into a single archive--to do this an archiving program is used first, such as tar.