1. carefully showing or explaining each part or stage of something
explain something to someone by providing a step-by-step breakdown
A step-by-step breakdown of something is an explanation or instructions that are reduced to their most essential, simplistic or main points. You might have a step-by-step breakdown of accounts for example or a step-by-step breakdown of instructions to follow. Step-by-step breakdowns are usually used when there is a lot of information to take in or when the sequence of steps is important to follow.