The companies tab allows you to find and follow bigger
companies. You may want to follow some key companies in order to be
better integrated with the industry and stay on top of the latest
news.
You'll want to make sure you do this because clicking through to
the company page will show who else is in your network is connected
to the page - this is huge for personal branding because you'll
want people in your industry to recognize your face everywhere.
You can also create and add your own company page from this section
and start getting "followers".