It locates quotations from the Bible.
The Biblical verses are preceded in the Talmud text by a small circle.
Wherever such a verse is identified, a reference will be placed in the narrow margin that separates the Talmud from the Rashi or Tosafot section. Where there is no bordering Rashi or Tosafot column, the Torah Or reference will be placed in the outer margin.
The references are to the standard (Christian) chapter divisions of the Bible. No verse numbers are indicated.