Redundant text is a bane of technical writing. It’s when you add words that repeat what you just said. I wrote about this clear back in 2010 here and here. Use the Search… box near the upper right corner of the site to find several more posts on the subject. That’s how bad redundancy is! Anyway, I just ran into an Adult Children comic that uses some obvious examples to give you the idea.
Those were pretty obvious, but it’s easy to be redundant accidentally. For example, don’t say “do it over again.” Don’t say “return back.” Be alert and you’ll find lots more.