What does it mean that sequential versus parallel steps?

Some steps must happen in order while others can happen simultaneously.

Example: You are preparing a dinner for eight people. The recipe has twenty steps, and you treat them as a linear list: chop vegetables, then boil water, then marinate meat, then preheat the oven, then set the table. Dinner takes three hours because you never let two steps overlap. Your partner walks in and starts setting the table while you chop vegetables, boils water while the meat marinates, preheats the oven at the very beginning because it requires no prior output. The same twenty steps now finish in ninety minutes. Nothing about the tasks changed. What changed was the recognition that most of those steps had no dependency on each other — they only felt sequential because they were written in a list.

Try this: Choose a workflow you repeat at least weekly — a morning routine, a meal prep sequence, a work session setup, a weekly review. Write down every step in the order you currently perform them. Now, for each pair of adjacent steps, ask: Does step B require the completed output of step A? If the answer is no, draw a parallel bracket around those steps — they can happen simultaneously. Redraw the workflow as two tracks: one for steps that must be sequential (each depends on the previous), and one for steps that can run in parallel with other steps. Estimate the time savings. Try the parallel version once and note what actually happens.