<em> text </em>tells the browser to render the text in a distinctive emphasized fashion. The HTML standard defines this as a logical style as distinct from <i> text </i> which is a physical style.
This is <em> style
The meaning is that the physical style directs the browser to display in an italic typeface whereas the logical style directs the browser to display with a distinctive emphasis leaving it to the browser to decide how this is achieved (underlining or distinctive colour might be used).
Browsers
All browsers rendered the text using an italic typeface.