The sliding markers on the ruler are all for positioning paragraphs of text on a page. To set the indent for more than one paragraph, select all of the text you want to adjust before setting the indents.

The First Line Indent does just that: position the slider where you want the first line of a paragraph to start (or be indented).

The Hanging Indent is the triangle on top; it positions the start of the second and all following lines of text.

The Left Indent is the square underneath the hanging indent; it's used to move the hanging indent and first line indent together, keeping a constant space between them.

The Right Indent positions the right indent of a paragraph.

You can move indents into the margins of a document.

You'll get to try all of these in the practice session.