The division of feasts:

1) Saturday שַׁבָּת Shabbat

2) New Moon ראׁשׁ חדֶשׁ Rosh Khodesh

3) Passover פֶּסַח • חַג הַמַּצוֹת  Khag ha-Matzot • Pesakh

4) The Feast of Weeks חַג הַשָּׁבוּעוֹת Khag ha-Shavuot

5) Sukkot חַג הַסֻּכּוֹת Khag ha-Sukkot

6) Day of shouting/raising a noise יוֹם תְּרוּעָה Yom Terua

7) Day of Atonement יוֹם כִּפּוּרִים Yom Kippurim

8) Purim פּוּרִים Purim

Khag ha-Matzot, Khag ha-Shavuot and Khag ha-Sukkot are known as Khag חַג,  which means the feasts of holy worship assembly מִקְרָא קדֶשׁ Mikra kodesh or pilgrimage feasts.
Collectively these feasts are referred to as Thrice (three times) - שָׁלשׁ רְגָלִים Shalosh regalim, because during the existence of the Temple it was an obligation that each Israelite male must make a pilgrimage (three times per year) to Jerusalem to celebrate these three pilgrimage feasts.
The aim of these worship assemblies was to strengthen the sense of brotherhood, belonging and friendship within the people of Israel.
The worship in the Temple of God, the splendor of the Temple and  the preaching of the priests and prophets all strengthened the People of Israel in their faith, and tied the People of Israel to the kings from the house of David.
All of the above mentioned feasts, apart from Purim, have their origin in the Books of Moses.
Purim is celebrated as a reminder of historical events.