Use shortcodes to represent any kind of content or programming code within your contents.
The shortcode structure is like this:
[name_of_shortcode attr1="value 1" attr2="value2" ...]
Sample (contact form):
[forms slug="home-contact"]
slug: is the attribute name
home-contact: is the value for attribute slug
Note: Some Shortcodes don't need any attributes.
To see the available Shortcodes, go to: admin->settings -> shortcodes