Just diagnosed teacher

[Kkmom]

Hello All - Good to be among teachers. I am a retired middle school teacher and librarian. I am also newly diagnosed. Routine mammo on December 14th and lumpectomy on December 27th. This past Thursday, I went to oncologist and will be starting chemo soon.
I am estrogen +, progesterone + and Her2 + Neu.
My tumor was 2.00 cm, stage II

Does anybody know what it means on the pathology report it says:
Her 2+/ Neu Ki-67 - proliferation rate is 18%. I do not understand the proliferation part.