When I tab, my whole document is indenting. Why?

This uses Word's AutoFormat feature. To turn that feature off

1. Open Word
2. Open File -> Options
3. Go to the Proofing menu
4. Click AutoCorrect Options
5. Click the AutoFormat as You Type tab
6. Uncheck Set left- and first- indent with tabs and backspaces in the Automatically as You Type section
7. Click OK