Numbers a figure and makes it referable, replacing the old $\label{fig:1}\nonumber$ trick, which relied on MathJax numbering inline maths—something MathJax 3 no longer does at all, so every \ref to a figure had started printing (???).

Put it where the number belongs, in the caption:

[[File:cou1-standardDevSize.png|300px]]<br>
<small>Figure {{figlabel|fig:1}}: Standard deviation of the average.</small>

It counts figures in order of appearance, prints the number, and drops an anchor named after the label so that {{figref}} can link back to it. Refer to it with {{figref|fig:1}}.

The counter is a Variables variable, so numbering is per page and automatic: insert a figure and the ones after it renumber themselves.

See also {{figref}}.