בָּרוּךְ אַתָּה ה׳ אֱלֹקינוּ מֶֽלֶךְ הָעוֹלָם
הַמּוֹצִיא לֶחֶם מִן הָאָרֶץ.
Baruch Atah Adonai Eloheinu Melech ha’olam
Blessed are You, Infinite One,
ha’motzi lechem min ha’aretz.
who brings forth bread from the earth.
R. Jacob ben Asher, Tur: Orach Chaim 271 (ca. 1300)
In general when faced with more than one food we first say the blessing on the species that comes first in the list of the Seven Species (wheat, barley, grapes, figs, pomegranates, olives, dates). As such, we would usually say the blessing on the bread (wheat) before wine (grapes). But since we must say kiddush before eating bread, we have a dilemma of precedence. So, the Yerushalmi [the Jerusalem Talmud, redacted around ca. 400 CE] suggests covering the challah to hide it while we drink the wine first.
R. Isaac Luria, Sha’ar Ha’Mitzvot: Parashat Eikev (16th Century Kabbalist)
Bread (לחם) and salt (מלח) are both representations of the divine; salt is divine severity and bread is divine kindness. We seek to overpower the severity of the salt with the kindness of the bread. Therefore, our custom is not to sprinkle the salt on the bread, but instead to dip the bread into the salt — kindness over severity.
שולחנו מכפר עליו: בהכנסת אורחין.
Rashi on Chagigah 27a
A person’s table atones: through hachnasat orchim, the welcoming of guests.