It's nothing.
When collecting papers, there are various sources, such as PDF documents and web pages. When we put these various materials directly into the Word document, there is often a problem: when we put the text content into the Word document, we will also bring the format of the text into the document, even including pictures. This will bring difficulties to our further typesetting. Therefore, these additional information must be deleted.
After copying the data, select Edit/Paste Special in Word, select the unformatted Unicode version in the pop-up dialog box, and click OK to eliminate the formatting of the text.
However, although the format has been eliminated, another common problem has come again: there are too many paragraph marks (or manual line breaks or spaces) in the text. The original solution is to delete it manually! However, there are often hundreds of such symbols, and manual deletion is too slow and troublesome. There is a faster way in Word. Let's take deleting a paragraph mark as an example. Press Ctrl+H to open the Find and Replace window. Click the Advanced button to display the search options, then place the cursor in the Find box, click Special Character/Paragraph Mark, and leave the Replace box blank. Then click "Replace All".