<DL ...> was originally intended for (and is still very good for) making lists of terms and their definitions.
this code
produces this
<DL>
<DT>flame
<DD>an ugly argument in a newsgroup
<DT>spam
<DD>annoying unrequested email
<DT>troll
<DD>someone who start flames
by posting stupid things
</DL>
flame
an ugly argument in a newsgroup
spam
annoying unrequested email
troll
someone who start flames
by posting stupid things
<DL ...> is useful for all sorts of lists. Any situation where you want to say "this is a thing, this is stuff about the thing" is a good time to think about using a definition list. For example, a definition list can be used for a performance script:
this code
produces this
<DL>
<DT>Mary
<DD>So what's going on tonight?
<DT>Dawn
<DD>Let's play some music
<DT>Jason
<DD>Cool man, let's jam!
</DL>
Use it.