CSS Flexbox: Centering Content Horizontally and Vertically

This CSS code snippet sets the 'display' property to 'flex', which creates a flex container. The 'flex-direction' property is set to 'row', which arranges the flex items in a horizontal line. The 'align-items' property is set to 'center', which vertically aligns the flex items in the center of the container. The 'justify-content' property is set to 'center', which horizontally aligns the flex items in the center of the container. Finally, the 'margin-top' property is set to 20px, which adds a margin of 20 pixels to the top of the container.