The 2080 Ti is a much bigger GPU with 4352 Cuda Cores (the things that do all the rendering work) vs 2944 Cuda Cores the standard 2080. It also has more AI and Ray Tracing hardware as well as more GDDR6 memory that is clocked faster.
The 1080 Ti had only 3584 Cuda Cores, no AI or Ray Tracing hardware and the same amount of memory but it was the older slower GDDR5X.