What does "single-piece flow" or "one-piece flow" development mean to you?

As the title states, "What does "single-piece flow" or "one-piece flow" development mean to you?". I'm currently reading the book, "The Phoneix Project" by Gene Kim, and I've learned a lot. In the book, it mentioned developing a single-piece flow development system. When you hear that, what does that mean to you? What are some tools/resources/procedures you use to do this? When those words come to me, I instantly think about Git, branching, features, merging, etc...