With Tags you can use some programming logic inside Liquid. E.g. to show content only under certain conditions, you’d use the if tag.
Input:
{% if site.name == "A beautiful site" %}
This is indeed one beautiful site!
{% endif %}
Output:
# This is only shown if the site's title equals 'A beautiful site' This is indeed one beautiful site!
Go to the Tags page to read the docs on Tags.