The |sinon filter displays the argument that is passed to it if the tag to which it is applied returns an empty result:
[(#TEXTE|sinon{"there is no text"})]
will display the contents of the #TEXTE tag if that field is not empty, otherwise "there is no text" if #TEXTE returns nothing from the database.
The filters argument can be more complex than just a simple text string:
[(#TEXTE|sinon{#INCLURE{fond=my_page, env, id_article}})]
See also
Other test filters
Logical filters