In typography you want to avoid single words as the last line of a paragraph and single lines of text at the beginning or end of a column or page. Why? A lonely single word at the end of a paragraph creates a visual interruption in the flow that breaks the reader’s focus. This break is caused by the unintended white space that calls more attention than necessary to the single word. Similarly, a line or word of text that jumps to the next page/column or starts a page/column should be avoided for the same reason.
As graphic designers, we adjust the space between words and/or letters to resolve these typographic problems as the final step in the design process. This is is important no matter if the project is a website design, PowerPoint presentation, report, brochure design, invitation or any other design that includes text.
So now to the definition and naming of these little nitpicks. There seem to be different opinions on what is called an orphan and a widow. The Chicago Manual of Style and Robert Bringhurst in the Elements of Typographic Style agree:
Widow: A paragraph-ending line that falls at the beginning of the following page or column, thus separated from the rest of the text. (They have a past but no future.)
Orphan: A paragraph-opening line that appears by itself at the bottom of a page or column, thus separated from the rest of the text. (They have no past but a future.)
You can call them whatever you want, maybe widphans or ordows? They are a problem and need to be fixed!