The The Berlin Method of filtration
article covers it.
Mostly just think of the lr
as an in tank filter which your bacterial colony resides in. With proper water movement (15-20 times tank volume) it pushes the water through the lr
filtering out the nh3
and once mature even no3
Main advantage is since it's in the tank and not external i.e. sump/canister/ect... a good clean up crew (snails/hermits/sea stars/ect...) can keep the lr
clean thus reducing your maintenance and enjoy the tank more.
Other advantage is lr
typically comes with tons of other live hitchhikers
that are usually beneficial.