For edp458

This is a good explanation of how the e-unit works (the relay looking structure you mentioned).
https://dfarq.homeip.net/how-does-a-lionel-e-unit-work/

Sounds like you're new to this. Below is a link to an old Popular Science reference article from 1964 that gives a good basic explanation of some parts and some fixes for simple problems. This will give you a starting point if you run into additional issues.
https://archive.org/details/PopularScienceReferenceLibrary15CommonRepairsForElectricTrains1964/page/n5