This indicates whether a given MAC address entry was learned dynamically through normal traffic flooding, or configured statically by an administrator. An admin auditing MAC forwarding tables for potential MAC-spoofing or unauthorized static entries would filter specifically for static(2) entries, since those were deliberately configured rather than learned automatically and deserve a closer look if unexpected. A value of dynamic(1) on an entry the admin doesn't remember statically configuring would simply be normal learned traffic and not cause for concern.