I'm no expert on the name, but as I understand it Narrm is the traditional name for the CBD of Melbourne and it's been getting more and more use lately.

Invasion day is a more accurate name given to Australia day which falls on the anniversary of colonial settlers arriving in what is now Sydney. The rally serves to push for the date to be changed to one more appropriate to celebrate, though there is also a movement to abolish it entirely.

It's also used to spread awareness of other issues faced by Aboriginal people, to demand truth telling from the government and fair recognition of the true owners of the land.