Introduction

As explained by Vitalik Buterin:

Both multisig wallets and social recovery wallets rely on a concept of guardians: a set of N addresses, typically held by other people, of which any M can approve an operation (e.g., one could set N=6 and M=4). In the case of a multisig wallet, each transaction requires the approval of M out of the N guardians. In the case of a social recovery wallet, there is a single key that can sign transactions, but if that key is lost, M out of the N guardians must sign a message to reset the key.

How I think about choosing guardians for multisig and social...reddit

Good to know: Tyron Social Recovery requires an absolute majority (at least half of the guardians plus one) to recover the account.