The Uruguayan carnival lasts forty days and is a competition: the groups perform night after night at the Teatro de Verano and on neighbourhood stages, and a jury decides the ranking.
Murga is choral singing with political satire; candombe is drums. They are different traditions sharing the same calendar — and the Desfile de Llamadas is the moment candombe takes the street.
If you are only going once: pick a neighbourhood tablado on a weeknight and the Desfile de Llamadas the following weekend.