While you can use empty columns (like <div class="column"></div>) to create horizontal space around .column elements, you can also use offset modifiers like .is-offset-x:
If you want a column to only take the space it needs, use the is-narrow modifier. The other column(s) will fill up the remaining space.
Narrow column
This column is only 200px wide.
Flexible column
This column will take up the remaining space available.
<divclass="columns"><divclass="column is-narrow"><divclass="box"style="width: 200px;"><pclass="title is-5">Narrow column</p><pclass="subtitle">This column is only 200px wide.</p></div></div><divclass="column"><divclass="box"><pclass="title is-5">Flexible column</p><pclass="subtitle">This column will take up the remaining space available.</p></div></div></div>
As for the size modifiers, you can have narrow columns for different breakpoints: