The output is [[sorted|Order of Tagged Tiddlers]] using the tag's <<.field list>> field and the tiddlers' <<.field list-before>> and <<.field list-after>> fields.
The behaviour when <<.place T>> is empty depends on the settings of the <<.place S>> optional suffix:
* if <<.place T>> is missing and <<.place S>> is either missing or set to "loose", then the output of `tag` is empty, and the output of `!tag` is a copy of the input.
* <<.from-version "5.1.14">> if <<.place T>> is missing and <<.place S>> is set to "strict", then the output of both `tag` and `!tag` is a copy of the input