means A pre-made pattern, form, or layout that you fill in or copy from, so you don't have to build the whole thing from scratch each time.

from From the older English 'templet,' a thin gauge or pattern used by carpenters and masons to shape repeated parts. The spelling drifted toward 'template,' likely pulled by the look of words like 'plate.' The deeper root is probably the Latin 'templum' — yes, the same family as 'temple' — which originally meant a space marked out for observation or building, by way of a related sense in French. So a template was always about laying out boundaries before the work begins.