A Phrase is a text block that is indexed from your website. Phrases can range from one word to a group of words and include things such as buttons, headings, descriptions, reviews and widgets. All of these use text, so when the Localizer platform analyzes your site content, these are all detected as phrases and can be translated.
One way to get an understanding of how Phrases work is to view your site using Visual Translator. Select Edit Mode and all phrases will be outlined in text boxes.
You can manage your phrases in bulk on the Batch Translator tab of your website and sort them by their translation status; translated, untranslated or ignored. Batch Translator allows you to translate (or un-translate) large amounts of phrases with the simple click of a button.