This is the text alignment or justification. If you want all of the text to line up on the right but be uneven on the left, then you would "align right" when typing. If you want all of the text to line up on the left AND right sides of the page, then you would justify the text. Just remember, if you justify text, it lines up on the ends but has strange spacing in the middle. In MS Word 2007, the icons for this function are represented by small straight lines that are lined up differently, and they are located right above the "paragraph" menu on the home page.
As used by Microsoft Word, the feature that forces every line to end evenly at the right margin is called right aligned. In right aligned texts all the lines end evenly at the right hand margin. Opposite of right aligned is left aligned. In this case all lines begin at the left margin but they need not end end evenly at the right margin. In both right aligned and left aligned text a line contains as many complete words as it can accommodate. When the last word in a line is too long to be accommodated in it, the next line is started.
Word processing also provides a feature in which lines are aligned both at left and right margins, except for the last line in every paragraph. The last line of a paragraph is always aligned on the left hand side, but on the right hand side it may end anywhere depending on number of characters in the line. This is called justified text.
The term justified has been borrowed from printing trade, which classified text as left justified, right justified, and fully justified. Justified as used in word processing corresponds to fully justified of printing trade.
Word processing has capability of another type of alignment of lines called centered. In this type of alignment, there is gap from margin on both left and right side of every line.