Eight of these are in pairs, giving you control of delay time and feedback level for each of the four taps.
The four taps let you feedback sound between the two stereo channels. The left-to-left and right-to-right taps give you a normal stereo delay. The left-to-right and right-to-left taps allow you create ping pong style delays. By mixing all four, you can get some spacious stereo spread effects.
The last control in this group, 'Feedback', sets the overall feedback level. Effectively it scales the four tap level controls.