Globale Texte are as the name suggests elements that do not have a place in other Features styles, and which appear globally throughout the site. A good example is if your site has a different name in French and in German. Create an entry in Globale Texte, called for example 'Sitename'. Then you can call this entry in your title tag with echo TRANLSATIONS::GetInstance()->GetTranslation('Sitename'). ZMS will check which language is active and output your correct language version.
Globale Texte can be used even if your site is single language. For example if you have a global footer that you want to make editable, you can use Globale Texte entries rather than creating a new Feature style.