Look up indentation in Wiktionary, the free dictionary.
In the written form of many languages, indentation describes empty space, a.k.a. white space, used around text to signify an important aspect of the text such as:
Many computer languages use block indentation to demarcate blocks of source code.
Indentation is essentially the same regardless of whether the writing system is left-to-right (e.g. Latin and Cyrillic) or right-to-left (e.g. Hebrew and Arabic) when considering line beginning and end. For example, indenting at the beginning of line means on the left for a left-to-right script and on the right for right-to-left script.
Indent is both a noun and a verb. The verb is the act of formatting text to be indented whereas the noun refers to the resulting empty space.