Gets a value from a relationship based on its ID. This is like a nicer-to-read single tag version of the Get_Content Tag.
featured_post: 4e82a520-275f-11e6-bdf4-0800200c9a66
{{ featured_post | get('title') }}
{{ Statamic::modify($featured_post)->get('title') }}
Featured Post Title
The above is equivalent to doing this:
{{ get_content :from="featured_post" }} {{ title }}{{ /get_content }}
<s:get_content :from="$featured_post"> {{ $title }}</s:get_content>