Basic link content gets columnized automatically, as does widgetized content. While this automatic column structure takes care of most use cases, sometimes you want more advanced column structures with uneven columns. The columns shortcode gives you this ability. Recommended usage is within a text widget or content override.
For example, the following:
[ubermenu-colgroup]
[ubermenu-col colspan="2"]
<h4>Column 1/2</h4>
Curabitur in enim ipsum. Tel congue purus pharetra. Nullam eget
malesuada justo. Sed egestas, velit vel aliquet vestibulum, urna
urna dapibus enim, non hendrerit lacus urna non justo. Aliquam
blandit magna eu enim auctor euismod.
[/ubermenu-col]
[ubermenu-col]
<h4>Column 1/4</h4>
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nunc auctor
dolor vitae felis accumsan.
[/ubermenu-col]
[ubermenu-col]
<h4>Column 1/4</h4>
Suspendisse ut purus nulla. Integer viverra diam sed augue pretium
iaculis.
[/ubermenu-col]
[/ubermenu-colgroup]
produces this layout:

Add up to 7 columns, set your colspans, et voila!