What exactly are side chains?

Question

Monero could implement side chains at some point. What exactly are they? Monero can exit and enter them, for example.

Answer 1

Side chains are blockchains that Monero can be moved to and from with a form of pegging.

Decentralized sidechains will need miners to secure the network for the same reason miners are needed to secure Monero. For this reason adding sidechains only make sense once the main chain has achieved a high enough hashrate to be very secure.

Federated sidechains have the potential potential to eliminate the need for a P2P mining network but at the expense of decentralization. Some level of trust would need to be put into 3rd parties with some sort of multi-signature setup.

Sidechains are often discussed as potential ways to allow additional features (but sometimes at the expense of security or centralization). Since Monero has an adaptive blocksize and privacy as a core focus there appears to be no immediate need to create a sidechain.

Monero research goals include sidechains that could bring many additional features to Monero in the future.