Variable tags are used to create new Liquid variables.

assign

Creates a new variable. Assignments can also use filters to modify the value.

Code
{% assign is_valid = true %}
{% if is_valid %}
It is valid.
{% endif %}

{% assign name = "dave bowman' | upcase %}
{{ name }}
Output
It is valid.

DAVE BOWMAN

capture

Captures the content within its block an assigns it to a variable. This content can then be rendered later using output tags.

Code
{% capture hello %}Hello, {{ user.fullname }}.{% endcapture %}
{{ hello }}
{{ hello }}
Output
Hello, DAVE BOWMAN.
Hello, DAVE BOWMAN.