Layer-2 scales Layer-1 by increasing capacity without significantly changing the security assumptions of the Layer-2. Although this does not change L1 itself, it does influence the general scaling design direction, generally pushing ethereum into a rollup-centric roadmap.
- Side-chains: EthHub, eth org
- State channels: EthHub, eth org
- Plasma (mostly deprecated): EthHub, eth org
- Rollups intro by Polynya
- Bridges: eth org intro
- L3 / validiums / volitations etc:
Refer to L2beat.com for an overview of active L2 scaling solutions.