The paragraph style called "Normal" is present by default in every document and has a special significance: it is the default style of paragraph formatting in the document. When you start entering text in a new document, the "Normal" paragraph style is automatically used for the text.

If you change the "Normal" paragraph style – for example, the line spacing – the line spacing of the entire text will be changed (except for paragraphs where you have set a different line spacing manually via the ribbon tab Home | group Paragraph). Furthermore, subsequent text will appear with this line spacing which you have defined in this manner as the new default spacing in the "Normal" paragraph style for the document.

If you want to apply a different paragraph style to your existing text instead of the default "Normal" style, select the text and follow the instructions in Applying paragraph styles.