.po files are files that are used to translate software apps into various languages. They are compiled as catalogs within the Gettext library, and you can edit them by hand, as text files, or even using an editor like Poedit.
Poedit lets you easily work with .po files, since you just have to translate, word for word, all of the terms and expressions used in the files original language.
You can also save translations to a database to use them later, and you can also bookmarks. The program can also be used to either edit existing catalogs, or create new ones.
Finally, this app is compatible with C, C , Java, Perl, PHP, Python, TCL and Delphi, it will let you update catalogs from HTML files, and it also gives you the option of compiling them in a .mo file, which, in the end, will be used in apps.