What does the “rod of an almond tree” in Jer 1:11 refer to?

In Jeremiah 1:11, what does the “rod of an almond tree” refer to? 11 Moreover the word of the Lord came to me, saying, “Jeremiah, what do you see?” And I said, “I see a branch of an almond tree.” 12 Then the Lord said to me, “You h…