There are a few types of duplicate content. One of the most common I see is duplicate page titles and meta descriptions.

这儿有一些复制内容的类型，最常见的复制页面类型是网页标题和网页描述标签重复。

youdao

Search engines will see the duplicate meta descriptions and sometimes judge a page as duplicate before they get to the actual page content.

搜索引擎会发现这些重复的描述标签，某些时候搜索引擎会在获取真实的页面内容之前就判定这是个复制的页面。

youdao

These factors include on-page factors, content, download time, duplicate content and URL issues, and off-page factors such as securing links from credible directories, websites, and maps.

这些要素包括站内优化、网站内容、下载时间、重复内容和URL；以及站外优化，与可靠的目录、网站和地图建立链接。

youdao

Xerox built machines that scanned a printed page of type using a photographic lens, and then printed a duplicate.

NEWYORKER: Creation Myth

Some Tumblr users are seeing their pages replaced with several dozen duplicate posts from a known hacker group, warning that deleting said message will delete the Tumblr page in question (it's unclear if this is actually true, but seems to be false in our testing).

ENGADGET: Hacker group rewriting Tumblr pages into a racist, anti-gay screed (update: Tumblr says it's fixed)