What is LFE on sub connections

A no-brainer to most on this forum, but I'd like to know what this connection does in any system, music or HT? My HT connection was set up from the receiver's sub out to the L/R line levelon the sub. That is what I was advised to do. But what is the LFE, and have I made the best connection for my HT system?
For music, what connection is best?
LFE is "Low Frequency Effects" which has to do with non-musical low frequency like earthquakes, thunder, etc. I believe the way you have it set up, both music related and Effects related low frequency will be delivered.

Depending on your speakers you may use your sub for both music and LFE, or only for LFE. For example my mains deliver flat response to 20HZ, so my sub is configured strictly for LFE.
The LFE input bypasses the sub's internal xover. You should use the LFE input when using an external xover like your receiver's sub out.

Does your question imply that your receiver has both sub and LFE outputs?

I must admit that I hadn't made such a distinction, often referring to my sub output as LFE. But I see that the manuals for my Proceed PAV/PDSD pre/pro label the outputs only as sub, with no mention of LFE. The balanced sub output from my PDSD goes to a Velodyne SMS-1 bass manager (room correction) then via balanced line to a Velodyne HGS-15. That configuration, crossed at 80 Hz, provides the felt more than heard sound of a big pipe being invoked as well as the high level low frequencies in films. So, is there a practical distinction except as a separate track in the film industry?

The sub itself has either LFE or standard inputs.