Is this necessary if using Electrum? Or are these 2 different kinds of wallets?
No, both are 2 different kind of wallets.
Electrum is standalone wallet. You don't need ledger to use electrum but you need electrum (or other supported wallet) to use the ledger.
Ledger is HW wallet (physical device) as such it needs an interface (a GUI which turns the coding to human understandable form) to communicate with bitcoin network and one them is electrum ( you can also use mycelium or the original ledger wallet app).
Check the ledger website for more details about supported wallets.