Question on Change Package Project Part 1- IP

Hello All,

I read in Change Package Project Part 1- IP MO copy from file to target DB.

But in Activity section, highlighted in yellow color, I see project already exist, switch set not to overwrite

My question : why it is saying project is already exit and which object are not overwriting ? are they not overwriting customization? what actual this step do ?

what Copying Change Package Project - Part 2 - IP and Copying Change Package Project - Part 3- IP. I am worried about customization.

Can some one explain