The Arizal taught that before creation, there was only the light of einsof. Hashem wanted to unveil his glory and needed to create humans with which to reveal His greatness. So He constricted His light, so to speak, and created an empty space in which He created all the worlds, synonymous with His attributes. Of course, without the constant connection and life force of the Creator, these worlds cannot exist. Therefore, even though, Hashem created an empty space, there must still be a trace connecting the worlds to Him. That trace is called a קו, a line, or רשימו, the imprint.
In Birkas Hashachar 5, Reb Nosson reveals that the verse Shema Yisrael, שְׁמַע יִשְׂרָאֵל, יְהֹוָה אֱלהֵינוּ, יְהֹוָה אֶחָד, has 25 letters in it, whereas the verse Baruch Shem בָּרוּךְ, שֵׁם כְּבוד מַלְכוּתו, לְעולָם וָעֶד, has 24 letters in it. I’d like to say that this is symbolic of the above teaching from the Arizal. What is Shema Yisrael? It’s affirming the oneness of God. It’s admission of nothing other than the Creator. That’s an aspect of einsof before the creation; total unity. Baruch Shem is more relevant to us. It talks about Hashem’s glory in the worlds, which is our avoda to reveal. The difference between the 24 letters in Baruch Shem and the 25 letters in Shema Yisrael is, of course, only one. This one represents the trace of einsof in this world that gives it vitality. I think that we express these two phenomenons in prayer often. First in Kaddish. The Kaddish starts off with יִתְגַּדַּל וְיִתְקַדַּשׁ שְׁמֵהּ רַבָּא (His great name should be glorified and sanctified). This is an exclamation of His greatness and oneness, even before creation. Then we praise Him by saying יְהֵא שְׁמֵהּ רַבָּא מְבָרַךְ לְעָלַם וּלְעָלְמֵי עָלְמַיָּא, (His great name should be blessed in all the worlds). Here we’re talking about His greatness after creation, in relation to the worlds. The same is true in the Kedusha prayer. The first proclamation we make is קָדוֹשׁ קָדוֹשׁ קָדוֹשׁ ה’ צְבָאוֹת מְלֹא כָל הָאָרֶץ כְּבוֹדוֹ, this is saying that Hashem is greater than any world can fathom. Then we say בָּרוּךְ כְּבוֹד ה’ מִמְּקוֹמוֹ, this means that Hashem is great from His place, meaning He, so to speak, has a place in the worlds.
What does this mean to us? The fact that we have a connection to einsof is why there can never be reason to despair. This is the source of all Teshuva. We humans, even when we’re dirtied from sin in the lowest of all worlds, are always connected to something out of this world. We might have to hush the Baruch Shem in silence most of the time, but we still must say it. We recognize that the Creator is beyond any comprehension, but we must also admit that we have a direct line to the highest places unimaginable.