Shortcodes
Shortcodes are Solodev's templating language — small [bracketed] tags that pull in data, control page flow, or render a widget, written directly alongside HTML in a page's markup. They're parsed server-side before a page is served.
[google_website_search google_cse_id="XXXXXXXXXXXXXXXXXX"]
Self-closing shortcodes look like [shortcode attr="value"].
Enclosing shortcodes wrap content and use an opening and closing tag: [shortcode attr="value"]...content...[/shortcode].
Double curly braces {{field_name}} are used to reference content fields within an enclosing shortcode, such as [repeater] or [entry]. The field names correspond to the fields available in your modules.
Categories
Writing your own
A website can register its own PHP file of custom shortcodes, on top of the built-in ones. See Building Custom Shortcodes.