Radak: Even though all Chagim are called Mo'adim ? "Eleh Mo'adei Hashem" (Vayikra 23:2), there is a Chag that is not Mo'ed, only Simchah ? a person rejoices, eats and drinks and it is called Chag, e.g. "va'Ya'as Shlomo ba'Es ha'Hi Es ha'Chag? Shiv'as Yamim" (Melachim I, 8:65). There is Mo'ed that is not Chag, e.g. "l'Olos ol'Mo'adim", "la'Mo'ed Ashuv Elecha" (Bereishis 1:14, 18:14), or any time that one sets for his friend. Therefore, it says "uv'Chagim uv'Mo'adim."

Malbim: "Chag" refers to Shavu'os, which is called Chag, for we bring Shalmei Chagigah on Shavu'os. "Mo'adim" refer to Rosh Hashanah and Yom Kipur, which were among the 190 days of Chinuch. Also then the Minchah for a bull and ram will be an Eifah, and a sixth of an Eifah for each lamb, like above (5). It did not need to teach the number (6) of lambs, for we know that Rosh Hashanah is Rosh Chodesh ¹ .