system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The practices/beliefs of the Jewish religion.
gpt
Judaism is a monotheistic religion - i.e., we believe in "One God", indivisible. The foundation of Judaism is found within the Torah (a.k.a. the old testament) wherein you will find every law (halachah) that a Jew must follow. These are referred to as "mitzvot". There are 613 Mitzvot. 
These concern everything from dietary law, to dress, to marriage and death. A significant portion of mitzvot concern laws related to the Sabbath.

The hebrew calender is neither lunar nor solar. Technically, it is a combination of both. There are 13 months but sometimes there is a leap month.

Jews are huge on life cycle celebrations (birth, bar mitzvah, marriage, death) and have many, many holidays. There is only one Jewish month without a holiday.

The most important holidays are pesach (passover) and yom kippur (the high holy days refer to the 10 day period before yom kippur).

Passover commemorates the exodus from egypt (moses and the israelites) and Yom Kippur is the day of atonement - supposedly, when God writes in the book of life your fate for the following year (this is why you atone).