urban renewal: The clearing and rebuilding and redevelopment of urban slums.
gentrification: The restoration of run-down urban*areas by the middle*class (resulting in the displacement of low-income residents)
urban renewal is just buildings that are dilapitated being reconstructed. it does NOT have to include any relation to the upper /middle class
gentrification is basically when a bunch of rich people come and renew the place with their money. This subjugates the lower class. (much similar to what is happening in redfern ftw)