The text is perfectly aligned on the left and right sides of the screen without jagged edges. This is the so-called fully aligned text, which is as easy to implement as right-aligned or center-aligned text.

The above English is not "fully aligned" because there is a space at the right end of the first line, which is not aligned with the letters of the second line.

In text typesetting, the default is always "full alignment", because once a word can't fit in one line, it will be placed in the next line, and the spacing between other words in the previous line will automatically increase to fill the blank.

Simply put, "full alignment" in Word means "alignment at both ends".