Okay, show of hands: How many of you remember being taught how to center text in typing class? (Alright, hands down. Those of you who responded with "Typing class? What's typing class?" have officially made me feel ancient.)
For you youngsters out there, here's how it went down: All of us typing students rolled a sheet of paper through the platen (look it up, kiddies) of the typewriter and spaced over to the center of the page 4.25" from each edge (using the tab key and space bar), calculated how many letters and spaces were in whatever phrase we wanted centered, divided by two, then backspaced from the center point by that many spaces.
Years later, it exhausts me just to describe it.
Fortunately, modern word processors like Microsoft Word make exercises like this obsolete. Oh, sure, you already know how to center text, right? But using center justification centers the text between the left and right margins. But what if you want to center text across another point on the page?
Answer: center tabs.