I have 2007 Chevy Aveo and I need to replace this part but don't know what it is called. It's a "t" square that water runs through one part and air through the other and connects to the throttle body
After doing some research, I think I found your part. See diagram below:
You can see that the little T-junction is part of the PCV hose assembly (item 21 in the diagram). Unfortunately, this means you can't source the part separately, you'd need to buy the whole PCV hose. The part number of the PCV hose is 96474643.