The new Send button makes it easier to share things privately with groups and individuals. Unlike the 'Like button', which is visible to all friends, the Share button allows users to send the links selectively. People will have the option to send your URL in an inbox message to their Facebook friends, to the group wall of any Facebook group they are a member of, and as an email to any email address.
The message will include a link to the URL specified in the send button, along with a title, image, and short description of the link. Users can specify what is shown for the title, image, and description by using Open Graph meta tags.
"The Send button is a social plugin that websites can use to let people send a link to a friend through Facebook Messages, post it to a Group, or email it to an individual. For example, if you see a Mother's Day gift idea on 1-800-Flowers.com, you can now send a message or email to your family members to discuss. Or say you're training for a marathon and you come across a great article about running shoes on The Huffington Post. Now you can share it with your entire running group in just one click," Facebook describes the Send button.
Moreover, websites can integrate the Send button on their websites that lets users send a link and a short message to the people that would be most interested.