Just read about the NIP-02 format that specifies an event called `contact list` for following profiles and receiving events from them. Each profile has a hex key, relay URL, and petname associated with it. The content of the event can be anything and should be ignored. Whenever a new contact list is published, it overwrites any previous ones. Users are advised to delete old contact lists once they have received a new one to prevent cluttering their databases with unnecessary data. The kind-3 event can be used for various purposes such as backing up and restoring contact lists, discovering and augmenting profiles, and relay sharing. It allows users to display a list of followed people by profiles they are browsing, make suggestions on who to follow based on the contact lists of others, and show data in different contexts. Additionally, it enables users to share full lists of contacts with good relays for each of their contacts, increasing censorship resistance. The petname scheme allows users to use local tables derived from other people's contact lists, which alleviates the need for global human-readable names. This is achieved by using a combination of internal and external contact lists, where the internal list contains the