These two names sound like they should be the same thing, and that mix-up is common enough that it's worth a clear side-by-side. They produce genuinely different output, and picking the wrong one is the most common reason someone's flipped text "doesn't look right."
Reverse Text takes your sentence and reads it backward, character by character — the letters themselves are completely untouched, only their order flips.
Every letter is still a normal, right-side-up letter. This is the mode to use when you want a genuine "read it backward" puzzle, or a palindrome-style effect, without any of the letters looking unusual.
Reversed Flip Text does the opposite. Each letter is swapped for its upside-down Unicode lookalike, but the original word order stays exactly as you typed it.
Notice the words are still in the same left-to-right order as the input — only the individual letter shapes are rotated. This is the mode people usually want for a stacked design, where a line of flipped text needs to still align visually under a line of normal text without the word order jumping around.
Reverse Text changes where the letters go. Reversed Flip Text changes what the letters look like. If you read your output and the words are in a completely different order but every letter still looks normal, that's Reverse Text. If the words are in the same order but the letters look strange, that's Reversed Flip.