[catsittingstill]

Left justfied text all lines up at the left margin, but the lines end at different places on the right, producing a ragged margin sometimes referred to as "ragged right."

Fully justified text lines up at both the right and left margins, usually by tinkering with spaces between letters and spaces between words.

(I tried to give examples, but spacing in the comment window is not the same as spacing in the post, so I had to delete them.)