A break is a way of escaping a loop. This is an extremely useful tool if you want to break execution of a loop when a certain parameter is met.
Example:
{% define $x = 1 %} {% loop product(current, name, desc) %} <div> <a href="{current.product_url}">{current.product_image_tiny}</a> <p><a href="{current.product_url}">{current.product_name}</a></p> <p>Part #: {current.attr_part_number}</p> </div> {% if $x == 5 %} {% break %} {% else %} {% increment($x) %} {% endif %} {% endloop current %}