ETH biggest problems is the low transactions per second:

1. Cardano adopts the proof of stake method. Not everyone can mine, only a few called slot-leaders. The time is broken into epochs and each epoch into slots (a short period of time in which a block can be created). The network elects a slot leader and that's the only one that can mine a slot. Slot leaders verify transactions and put them inside a block. The number of slots per epic can be varied and multiple epochs per epics can be run.
2. Cardano splits its network into multiple sub-networks using a method called RINA. Each node will be part of a sub-network.