Anything that doesn’t fall inside posts, pages or taxonomy goes into String Translation. This includes the site’s tagline, general texts in Admin screens, widget titles and many other texts.
A complex site may contain many strings to translate. Use the display filter, at the top of the String Translation page, to determine which strings to display.
Which strings to display – choose the translation status (everything, translation complete, translation needed or waiting for translator)
Strings domain – WPML organizes strings into different domains, making it easier to find a specific string. If, for example, you are looking for a widget string, select the Widgets domain
Search – you can enter a search value to narrow down specific strings