I do apologise for such a simple question but pretty much every website treats me as an expert modeller and does not explain the basics. Hopefully, you will have the patience...

I am building a Tamiya King Tiger and upgrading it over the stock elements at the same time. I got most of the "mechanical" upgrades that I planned to fit in (suspension, gearboxes, engines, idlers, wheels, etc.) but I recently discovered the existence of El-Mod and realised how many of R/C tankers use it. Just to be clear - I don't know what El-Mod EXACTLY is.. Is it a total substitute to the Tamiya electronics and steering modules (DCM etc.)? Does it add more possibilities and features (e.g. future planned smoke & lighting system upgrade)? Does it upgrade the whole sound system too?
I read that in general El-Mod is for more advanced modellers but (since I don't consider myself to be super-thick

I'd really appreciate any help here as wherever I go I find abbreviations and shortcuts of technical features I'm not familiar with (yet).
Thank you in advance -
Darek