A label serves as an organizer on the main Moodle page. It's often used to make heading to divide up content. Labels can be used to add text, images, multimedia and/or html code in between other resources in the different sections. It is a very versatile resource and can help to improve the appearance of a course if used thoughtfully.
Here's how to add a label in Moodle 2.6: http://youtu.be/QVIsMZ9ey5Y.