How many columns can bootstrap have?

Bootstrap's grid system allows up to 12 columns across the page. If you do not want to use all 12 column individually, you can group the columns together to create wider columns:

Does bootstrap have a grid system?

Bootstrap's grid system is responsive, and the columns will re-arrange depending on the screen size: On a big screen it might look better with the content organized in three columns, but on a small screen it would be better if the content items were stacked on top of each other. Tip: Remember that grid columns should add up to twelve for a row.

Does bootstrap XS 6 work on a larger screen size?

"Bootstrap grid classes work on all sizes above the size specified, so applying col-xs-6 will cause that element to also contain 6 columns on any larger screen sizes, like sm, md, etc". Can you explain how? Does it use javascript to achieve this?

What is Flexbox in Bootstrap?

Flexbox means we have options for changing individual columns and modifying groups of columns at the row level. You choose how columns grow, shrink, or otherwise change. When building grid layouts, all content goes in columns. The hierarchy of Bootstrap’s grid goes from container to row to column to your content.