Today, Friday and Saturday are Ember Days. Until I started doing some research on Lent, I had never heard of them before. Chad gave a good explanation here and Fish Eaters goes into great detail here (the following is just the basic information)
Four times a year, the Church sets aside three days to focus on God through His marvelous creation. These quarterly periods take place around the beginnings of the four natural seasons 1 that “like some virgins dancing in a circle, succeed one another with the happiest harmony,” as St. John Chrysostom wrote (see Readings below).
These four times are each kept on a successive Wednesday, Friday, and Saturday and are known as “Ember Days,” or Quatuor Tempora, in Latin. The first of these four times comes in Winter, after the the Feast of St. Lucy; the second comes in Spring, the week after Ash Wednesday; the third comes in Summer, after Pentecost Sunday; and the last comes in Autumn, after Holy Cross Day. Their dates can be remembered by this old mnemonic:
Sant Crux, Lucia, Cineres, Charismata Dia
Ut sit in angaria quarta sequens feria. Which means:
Holy Cross, Lucy, Ash Wednesday, Pentecost,
are when the quarter holidays follow. For non-Latinists, it might be easier to just remember “Lucy, Ashes, Dove, and Cross.”
These times are spent fasting and partially abstaining (voluntary since the new Code of Canon Law) in penance and with the intentions of thanking God for the gifts He gives us in nature and beseeching Him for the discipline to use them in moderation. The fasts, known as “Jejunia quatuor temporum,” or “the fast of the four seasons,” are rooted in Old Testament practices of fasting four times a year:
Thus saith the Lord of hosts: The fast of the fourth month, and the fast of the fifth, and the fast of the seventh, and the fast of the tenth shall be to the house of Juda, joy, and gladness, and great solemnities: only love ye truth and peace.
So today, Friday, Saturday are days of fasting. 1 regular meal and 2 small meals that add up to less than one whole meal. Friday is still a meatless day.