Mutual aid networks organise around a simple premise: neighbours helping neighbours directly, without waiting for a formal institution to coordinate the response. A shared spreadsheet, a phone tree, or a messaging group is often enough infrastructure to match someone who needs groceries picked up with someone nearby able to do it.
What keeps these networks functioning is not central control but a shared, fairly loose set of norms: ask clearly, offer honestly, and trust that the balance of giving and receiving will even out across the group over time rather than needing to be settled with any single exchange.
They tend to be most visible during a crisis, when formal systems are overwhelmed or too slow, but the more resilient ones keep a quiet baseline of activity going in ordinary times too, which is usually what allows them to scale up quickly when a harder moment arrives without much warning at all.