This template generates link targets for senses. Whenever a page of Wiktionary now has dozens of different senses for each language you can give the sense you want to link to an id. For example you want to link to the English word "house" in the sense of a "house music", which is number 13 in the list, you can use these links: house#English-genre of music and http://en.wiktionary.org/wiki/house#English-genre_of_music, after you have added this template:

before (not linkable):
# [[house music|House music]].
# {{senseid|en|genre of music}} [[house music|House music]].

The template will generate the following HTML:

<li id="English-genre_of_music" class="senseid">

Recommended: You can also use this template via the graphical editor by User:Yair_rand, which you can find under preferences -> Gadgets -> Enable definition editing options.