Shechina

Greetings Rabbi Shlita,
In honor of the holiday of Purim, they say, “Everyone who reaches out a hand is given a hand.”
I wanted to ask what is meant by the concept of Shekhinah? And also in the Sefirot (not necessarily the role of each one but in the overall idea), and especially when the Kabbalists direct their prayers, are they praying to the actual Sefirot?
I didn’t see any mention of this here on Shutim when searching for titles.