Entropy allows you to create new archives in different popular formats. Below is a brief description of the formats available, along with their pros and cons.
Currently one of the most popular archive formats. Most operating systems provide "out-of-box" tools for extracting zip archives. As a result, it is widely used for casually sharing files. Zip archives also support encryption.
A relatively new archive format, 7zip boasts fast extraction times and excellent compression ratios that are often better than zip. While tools for extracting 7z archives are available for all popular platforms, they aren't usually installed by default.
Tar archives ( also known as Tarballs ) have been traditionally used for creating archives on unix based systems. While tar archives excel at combining a large number of files into a single archive, they do not compress their contents. As a result, you often see tar archives combined with popular compressors like gzip and bzip2 to produce formats like tgz and tbz2.