During leap years on the Hebrew calendar, Purim is celebrated in the second month of Adar. The 14th of the first Adar is then called Purim Katan ("Little Purim" in Hebrew), and the 15th is Shushan Purim Katan, for which there are no set observances but a minor holiday aspect. Certain prayers, like Tachanun, are omitted. When 15th Adar I is on Shabbat, "Av Harachamim" is omitted. When the 13th or 15th Adar I falls on Shabbat, "Tzidkas'cha" is omitted at Mincha. Fasting is prohibited.
Things you should know about Purim Katan:
Should one make a festive meal in honor of Purim Katan, and is there any difference, being that this year, Purim Katan is on a Friday?
The Beis Yosef (697) brings the Rosh (Megillah 1:7), who rules that one doesn't have to make a festive meal during the first Adar. Tosafos (Megillah 6b) concurs with the Rosh.
The Rif (Megillah 6b) rules one should make a meal. The Ran says like the Rif.
In the last siman of Shulchan Aruch (OC 697), the Rema tells us that it's proper to make a small meal in honor of Purim Katan. However, it's not an obligation. The Mishna Berurah (697:5) also mentions that it is a good thing to do.
This year, because Purim Katan falls out on a Friday, we have a dilemma: The Shulchan Aruch rules (249:2) one may not partake in a meal on Friday that he is not accustomed to on a regular day. The Rema adds that if the meal's time is specifically on Friday, like a Bris or Pidyon Haben, one may make the special meal even on a Friday. The Biur Halacha adds one may make a siyum on a Friday. The question is, how do we view Purim Katan? For an exact approach, one's local Rav should be consulted.