What are the differences between Gmail labels and shared labels?
Gmail labels are synced back and forth between Gmail and Missive. Anyone you give full access to your email account on Missive will have access to the labels of this account. Note that this applies to shared accounts only, not shared addresses.
Labels under your Organization settings are Missive-only labels that are not synced to Gmail. Their purpose is to allow labeling non-email conversations, which include SMS, Messenger, Twitter, and chat-only conversations. Gmail labels cannot be applied if a conversation contains no emails. They are also valuable to label emails across multiple email accounts.