This weakaura is for content in Patch 8.2 Rise of Azshara.
This shows the current azerite essences you're using.
The number on icon shows the rank of that essence, or the stamina part. (Untested: I'm not 57 on HOA yet :/)
The large one is your main slot. You can change that display in conditional page.
I hope the tooltip can show the passive ability only on minor slots, but I can't test that on PTR.
Also I need a way to get the spellid of the passive ability, which I can't figure out how :/