A webhook (also called a web callback or HTTP push API) is a way for an app to provide other applications with real-time information. A webhook delivers data to other applications as it happens, meaning you get data immediately. Unlike typical APIs where you would need to poll for data very frequently in order to get it real-time.
Please see attached the instructions to set up webhooks from 1Centre to your other applications. You can also find this information via Settings > Integrations > Webhooks.