Amaro simply means bitter, and the various slightly bitter herbal liqueurs known as amari are very popular in Italy as a digestivo to help the pasta go down. Also see elisir.
Famous brands—each has a different secret recipe, with perhaps a score of different ingredients (herbs, roots, bark) added to fortified wines—include Fernet-Branca, Amaro Lucano, Ramazzotti, Averna, Biadina, Amaro Montenegro, Amaro Sibilla, Vespetro and Cynar. Foreign brands are also popular, such as Jägermeister and Unicum.
Many of which are very much an acquired taste (where we lived in Umbria, it used to be a poison known as Vipero, which had all the charms of a flat, warm rum and Coke and was so bad they stopped making it).
Amaro alle erbe alpine delle montagne di Cesana: from Piedmont, made with mountain herbs, is designated PAT.
Image by Shabbychef, Creative Commons License