Attribute:data-offset usage

In this what is the use of attributes=data-spy,data-target and data-offset

HTML5 Introduce this data atrributes called "Custom data attributes" or data attributes.

Custom data attributes:

are strings — you can store anything which can be string encoded, such as JSON. Type conversion must be handled in JavaScript.
should only be used when no suitable HTML5 element or attribute exists.
are private to the page. Unlike microformats, they should be ignored by external systems such as search engine indexing bots.

For more info follow the below urls:

http://www.sitepoint.com/use-html5-data-attributes/

Hope this helps!