What is the main use of CSS Flexbox?

The main use of CSS Flexbox is to manage one-dimensional layouts, which allows for the arrangement of items in either a row or a column. Flexbox provides a powerful and flexible way to align and distribute space among elements in a container, making it easier to design responsive layouts that adapt to different screen sizes and orientations. By utilizing properties such as flex-direction, justify-content, and align-items, designers can control the positioning and sizing of items, ensuring they look good in a variety of contexts.

In contrast, controlling text formatting typically involves using other CSS properties that are not related to the layout management capabilities of Flexbox. Creating 3D graphical layouts falls outside the scope of Flexbox, as it is primarily designed for two-dimensional (1D) alignment rather than complex 3D effects. Lastly, defining multimedia elements involves the use of HTML and other CSS properties to handle media such as images and videos, which is not what Flexbox is used for. Thus, the focus of Flexbox is clearly on managing horizontal or vertical layouts effectively.