LFE is the "low-frequency effects" channel. The LFE channel plus all bass (frequencies below the crossover setting in the AVR) from your other speakers channels are output through the "Subwoofer" output (sometimes incorrectly labelled the "LFE" output) on your AVR.
Subwoofers often have inputs labelled "LFE" in addition to a set of L+R RCA inputs. If your sub has an "LFE" input, that's what you connect to. If it doesn't have an "LFE" input - which is the situation you face - you should be able to connect to either the L or R RCA input, or to both inputs (using a Y-splitter). The owner's manual for the subwoofer should tell you which method to use.
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.