Google's Gary Illyes explained what he meant is the term "near duplicate content." Gary posted it on Twitter saying near duplicate content can be thought of as "a piece of content that was slightly changed." He added that it can also be near duplicate when the "it was copied 1:1 but the boilerplate is different."
Here is his tweet:
Think of it as a piece of content that was slightly changed, or if it was copied 1:1 but the boilerplate is different
— Gary Illyes ᕕ( ᐛ )ᕗ (@methode) June 11, 2017
So there are two forms:
(A) Someone who takes a piece content from one site and slightly changes it and posts it on their own site.
(B) They take all the content from one page and puts it on their own page but the boiler plate content in the header, footer, etc is different.
We see both of these forms a lot on the web.
Forum discussion at Twitter.
