Class:

span.blue
(-->)
<span class="blue"> <span>

.container
(-->)
<div class="container"> </div>

ID:

h1#title
(-->)
<h1 id="title"> </h1>

Siblings:

.uno+.dos
(-->)
<div class="uno"></div>
<div class="dos"></div>

Children:

.container>.row>.col
(-->)
<div class="container">
    <div class="row">
        <div class="col"></div>
    </div>
</div>

Attributes:

div[target title]
(-->)
<div target=" " title=" "></div>

div[target=bullseye title=myTitle]
(-->)
<div target="bullseye" title="myTitle"></div>

ex:

(-->)

Emmet.io (Docs)