Q. What is se’udah sh’lishit?
The three meals symbolise the three main themes of Shabbat – creation, revelation and redemption. Friday night celebrates the creation of the world, Shabbat morning the giving of the Torah, and Shabbat afternoon the serenity and spirituality of the World to Come.
Hence the z’mirot sung on each occasion are different and this is even reflected in their melodies; the Shabbat afternoon tunes have more pathos and poignancy.