Before you think I am writing about women who have lost their husbands, or children without parents I want to stop you there. Widows and orphans is a term used within design used to describe text that overflows into different pages or columns badly.
The Chicago Manual of style defines them as this:
Widow: A paragraph-ending line that falls at the beginning of the following page/column, thus separated from the rest of the text.
Orphan: A paragraph-opening line that appears by itself at the bottom of a page/column or a word, part of a word, or very short line that appears by itself at the end of a paragraph. Orphans result in too much white space between paragraphs or at the bottom of a page.
Basically they look bad and should be avoided.
After doing a bit of hunting around I discovered that Adobe InDesign has a very handy method of avoiding them. In the text box you want to adjust press Ctrl + Alt + K (Cmd + Opt + K on a Mac) and you get a very handy dialogue box. From there you can adjust the minimum number of lines of text per page. InDesign handles the rest.