Are you trying to say hot wallets or maybe software wallets? They are, yes. However, Electrum can be both a hot and cold wallet, meaning you can use it on an internet-connected computer or a permanently airgapped device. Bitcoin Core is a full-node client, which needs internet connection to update and sync the newest blocks. Electrum being a light client that doesn't require downloading the whole blockchain to work is easy to take offline. I think it's still doable with Bitcoin Core, and I could swear I saw an old guide for it in the past. But it's not user-friendly having a full client that is offline.