Notifications, order/status updates, version control integrations like GitHub webhooks.
Via SSL, token-based authentication in the request parameters or headers.
Centralized services like Zapier or tools tied to specific services/apps.
Libraries for Node, Ruby, Python etc. Services like IFTTT, Integromat support webhook channels.
Not necessarily, delivery is best effort. Might be delays depending on infrastructure.
For frequent updates, syncing multiple systems, improving response times over long/live polling.