It is connected to the High-Logic Font Management Service (fontservice) and acts as a doorway between the fontservice (running as administrator) and your user environment where your fonts are installed. It proceeded to do more harm than good - for all sorts of reasons - but mainly because it is a hugely inefficient way to format text.
The font tag was brought in early in HTML’s life to allow designers to change the size, typeface and colour of their text.
