Object removal solves the problem of moving subject matter being included in your images—think of passing crowds, vehicles, birds flying, or other annoying distractions. Obviously, a single shot taken at a specific time may be the perfect solution but it may not be practical or possible to wait for this.
To allow for perfect image alignment, use a tripod or ensure your camera is in a fixed position.
Take a pragmatic approach and be realistic. Scenes full of moving objects cannot be completely emptied, nor will stationary objects magically disappear (but can be made to using the Inpainting Brush tool later!).
To create an object removal stack:
From the File menu, select New Stack.
From the dialog, click Add to locate and select your images. Click Open to add the images to the stack list.
On the Layers panel, select the Median stack operator from the Stack operator pop-up menu on the Live Stack Group layer.