Three kinds of shuffle: reorder the words in a sentence, reorder a list of lines, or scramble the letters inside each word for a puzzle.
Shuffling words reorders the tokens in a sentence and is the basis of a sentence-reconstruction exercise: hand someone the shuffled version and ask them to rebuild it. Shuffling lines randomises a stacked list, which is how you draw a random order for a rota, a playlist or a presentation running order without picking favourites. Shuffling the letters inside each word leaves the words in place but scrambles their spelling, producing the classic word-jumble puzzle where the sentence structure is still visible but each word has to be decoded.
The shuffle uses the Fisher-Yates algorithm, which produces every possible ordering with equal probability. The common alternative, sorting with a random comparator, looks like it should work and does not: it biases certain positions, and with some sort implementations it can return the original order far more often than chance would suggest. That bias does not matter for a party game but it does for anything where the fairness of the draw is the point. Letter shuffling deliberately skips one-character words and leaves punctuation attached, so the shape of the sentence survives.
It uses Fisher-Yates, which gives every ordering an equal chance. That is not true of the common trick of sorting with a random comparator, which is measurably biased.
Letter shuffling skips words under two characters, and any short word can shuffle back into its original order by chance, that is a property of a genuine shuffle, not a bug.
No. A shuffle discards the original order, so keep a copy of your input if you need it. Refreshing produces a different arrangement, not the original.