Overview
This tag's only purpose is to fetch the number of the entries in a collection that match your set of filtering parameters without the need for a tag pair/loop.
Example
There are {{ collection:count in="pogs" }} pogs in this site.
There are 6201 pogs in this site.
You could do the same thing inside a regular collection tag by aliasing the results to a single variable and using the count modifier.
{{ collection:blog as="entries" }}There are {{ entries | count }} pogs in this site.{{ /collection:blog }}
Parameters
in|from
The collection in which to count entries.
*
All parameters available on the collection tag are available.