Learn in the textbookCoding Conventions and Structuring
DefinitionIndentation (字下げ) is the practice of adding spaces at the start of lines so that blocks of processing and nesting levels are visible on sight.
ExplanationLines inside a conditional branch or a loop are shifted one level to the right, and lines at the same level start at the same position. In most languages changing the indentation does not change the result, but some languages such as Python use indentation to decide where a block begins and ends. Either way, block boundaries are clear at a glance and misreadings become less likely.
AnalogyIt works like an outline in which sub-items are written slightly to the right under a main item, so you see at once which sub-item belongs to which main item.
Memory hookThe Japanese name literally means "lowering the characters": the act of pushing the first characters of a line to the right became the name itself.