I have seen many people writing "#someword" as a shortcut for
<div id="someword"></div>
and also ".someword" as a shortcut for
<div class="someword"></div>
Do you know how to do that? Thank you for your help!
The functionality is build in. You do not need any additional extension. As soon as you save your file as a *.html you can use the #someword syntax and the Emmet Abbreviation pops up automatically-