Above the document itself, you will find the horizontal ruler, which is mostly called the ruler later in the manual. This bar displays the indents and tabs for the current paragraph (or any paragraphs currently selected).
Indents and tabs are not only displayed there, they can also be changed via the mouse. You will learn how to do this in the sections Indents and Tabs.
Tip: You can enable or disable the ruler in the ribbon interface via the command View | Horiz. ruler 
(also View > Horizontal ruler in the classic menu interface).