If you make headings bold and bigger by hand, every change means reformatting dozens of headings — and you cannot generate a table of contents. Styles fix both.
In this article
1. Apply heading styles
Put the cursor in a heading and click Heading 1 on the Home tab (Ctrl+Alt+1). Sub-headings get Heading 2 or 3. Body text stays Normal.
2. Change the look once
Right-click Heading 1 in the Styles gallery → Modify: font, size, colour, spacing. Every Heading 1 in the document updates instantly.
3. Insert the table of contents
Place the cursor where it should go → References → Table of Contents → Automatic Table 1. Word lists every heading with page numbers, and each entry is a clickable link.
4. Keep it up to date
After editing, click the TOC and choose Update Table → Update entire table (or press F9).
5. Navigate and reorganise
View → Navigation Pane shows every heading. Drag a heading to move the whole section with its content.
6. Number the headings
Home → Multilevel List → choose the style linked to headings (1, 1.1, 1.1.1). Numbers update automatically when sections move.