When multiple files are open, scrolling can be synchronized by right-clicking on the scrollbar and selecting Synchronize Scrolling. Once enabled, whenever one window is scrolled (either via the keyboard or the mouse), all other file windows are also scrolled by the same amount.
Horizontal and vertical scrolling are separate. Enabling synchronized scrolling by right-clicking on the vertical scrollbar will only synchronize vertical scrolling. If you also want horizontal scrolling to be synchronized, you also need to right-click on the horizontal scrollbar and select Synchronize Scrolling.
Synchronized scrolling only applies to multiple file windows - it does not apply to the directory listing.
This is different to the synchronized scrolling which is available when the file view is split.