By default, text at the start of a line (or after only white space) represents an html tag. Indented tags are nested, creating the tree like structure of html.

Pug also knows which elements are self closing:

Block Expansion

To save space, Pug provides an inline syntax for nested tags.

Self Closing Tags

Tags such as img, meta, and link are automatically self-closing (unless you use the XML doctype). You can also explicitly self close a tag by simply appending the / character. Only do this if you know what you’re doing.

Rendered Whitespace

Whitespace is removed from the beginning and end of tags, so that you have control over whether the rendered HTML elements touch or not. Whitespace control is generally handled via plain text.