The Reform Paragraph command re-formats the selected paragraph of text so that all the lines in the paragraph are as wide as possible, within the margin width for the current file type.
If you have an insertion point selection, then the enclosing paragraph is reformed. If more than one paragraph is selected, then all the paragraphs in the selection are reformed.
If the first line of the paragraph is indented, then all subsequent lines in each paragraph will be indented by the same amount.
A paragraph of text is assumed a series of lines, bounded by blank lines.
You can specify the margin width in the File Type Options command under the current file's file type.
For example, before running Reform Paragraph:
The quick brown
After running Reform Paragraph, the lines are made as wide a possible within the margin.
The quick brown fox jumped over the lazy dog, and other mysterious sentences.