The longer answer
A shared inbox replaces the classic '[email protected]' email address — where everyone is CC'd, nobody knows who's responding, and half the threads are answered twice while the other half not at all.
The core ideas are simple: every conversation is visible to the whole team; conversations have status (open, pending, resolved); anyone can claim or reassign; replies are sent from the team identity, not a personal email.
Modern shared inboxes also bring messages from chat widgets, WhatsApp, Instagram DMs and other channels into the same view. Whether a customer reached out via your chat widget at 11 AM or by emailing support@ at 3 AM, both land in the same inbox, in front of the same team.
This pattern is the right tool for teams of 1-20 people doing customer-facing work — support, sales, success. At 30+ agents with strict workflow needs, you might graduate to a full helpdesk; below that, shared inbox is the answer.