The Context-Sensitive taskbar is a new feature that allows for easy access to the tools Photoshop thinks you’ll need at different stages in your workflow. After you make a selection, the new taskbar will appear and give you the option to launch Generative Fill (if you don’t see the task bar go to Window > Contextual Task Bar to turn it on). The taskbar automatically positions itself to the bottom of the selection, but this can be annoying as it obscures other details. You can click the three-dot icon in the bar to pin it elsewhere. Alternatively, launch Generative Fill by going to Edit > Generative Fill (having first made a selection).