Hi Twist
I believe that file contains all of the modules built for that kernel. Once you've downloaded the file:
tar xf modules.tar.gz
cd lib/modules/4.19.81-piCore
There you will find some useful files about the modules:
modules.builtin: These modules are already built into the kernel.
modules.order: This is the list of external modules built for this kernel. It includes their path so you know where to find them.
modules.dep: Module dependencies. Each line contains ModuleName: followed by its dependencies, if any.
modules.alias: This file can help you track down the correct driver if you know the hardwares Vendor ID and Product ID.
modules.symbols: If you get symbol not found messages in dmesg, search for it here. It may point to a missing module.