bootstrap/docs/layout/containers.md

layout	title
page	Containers

Bootstrap requires a containing element to wrap site contents and house our grid system. Choose from the fixed or fluid width variation.

Use .container for a responsive fixed width container. This will center content withing the viewport and apply the appropriate width for a given device size. Containers can be nested, but be aware that most layouts don't require it.

{% highlight html %}

...

{% endhighlight %}

Use .container-fluid for a full width container, spanning the entire width of the viewport.

{% highlight html %}

...

{% endhighlight %}