Final answer:
In word processing, centering is the term used when margins are equally distanced from both the left and right sides.
Step-by-step explanation:
In a word processing document, bringing the margin in an equal distance from both the left and right sides is called centering. This is different from justification, which adjusts both the left and right edges so the text forms a straight line on both sides, and different from indentation, where only the first line or an entire paragraph is moved inward from the left margin. Alignment typically refers to how text is aligned with one margin or the other - left, right, or centered.