The user interface of most of LibreOffice is very similar across its modules:
Menu Bar
At the top of the application, there is the menu bar which gives access to almost all functionality of LibreOffice. The menu bar can be customized to include more or fewer functions. You can also add and remove menus.
Toolbars
By default, the toolbars are positioned directly below the menu bar. The toolbars comprise the most used and most important items of the module.
To dock a toolbar to any other side of the window, drag it to the right position. To make a toolbar float, drag it into the middle of the window. They can be customized to include more or fewer functions. You can also add and remove toolbars.
Side Bar
By default, the side bar is positioned at the right side of the LibreOffice window. On the first start of LibreOffice, it is only visible as several icons stacked vertically. Clicking one of the icons opens a panel with more elements. Click the icon again to close the panel. Similarly to the toolbars, the side bar comprises the most important functions.
To dock the side bar to the left or right side of the window, drag it to the right position. To make the side bar float, drag it into the middle of the window. To hide the side bar, click the vertical arrowhead button on the document-facing side of the side bar.
You can hide or show side bar panels but cannot customize their functionality.
Statusbar
The statusbar is displayed at the bottom of the window. It mainly shows information about the document, such as the number of words (in Writer) or the sum of values of selected cells (in Calc). However, it can also be used to change the zoom or language settings. Many elements open additional menus or dialogs on left click, right click, or double click.
For more information on customizing LibreOffice, see Section 9.6, “Customizing LibreOffice”.