The 613 commandments refers to a series of commandments, or mitzvot, that are specified in the Torah, which is the major holy text of Judaism. These include 365 negative commandments, or things that shouldn't be done, and 248 positive commandments, or things that should be done. The 613 mitzvot also include the Ten Commandments that are found in the Book of Exodus in the Bible.
The 613 mitzvot are divided into three main categories: laws (mishpatim), testimonies (edot) and decrees (chukim). There are many varying interpretations of what the exact 613 commandments are, but the most widely accepted classification comes from 12th-century Rabbi Moshe ben Maimon, known as Maimonides, who codified the mitzvot in his 14-volume Mishneh Torah.
A large portion of the mitzvot are related to the Second Temple, which stood in Jerusalem until it was destroyed by the Romans in 70 A.D. As a result, these mitzvot can no longer be practically observed. For example, one of the mitzvot from the Book of Deuteronomy says that no one should plant a tree in the temple courtyard. Some estimates hold that there are 77 positive and 194 negative commandments that can still be observed today, and 26 of them only apply within Israel.