The style associated with the shell you choose for your document determines how the text in your document is indented. With many styles, the Body Quote and Centered tags provide additional indentation from both margins, and lists are automatically indented. Also, the Tab key usually enters a 2-em spaceHorizontal.tex, with which you can add to the specified paragraph indentation.
If the indentation specified for a particular tag is not what you want, you can change it by changing the paragraph specificationsChanging_paragraph_specs.tex for the tag.
You can suppress indentation for an individual paragraph by inserting a horizontal spaceHorizontal.tex of noindent at the start of the paragraph.