Platform events enable you to deliver secure, scalable, and customizable event notifications within Salesforce or from external sources via a Message bus. PushTopic events track field changes in salesforce records and are tied to salesforce records. and Change Data Capture events which are the newest edition of the streaming events offered on the lightning experience. Have a detailed look at salesforce application development services and events.
Source: Platform Events Vs. Push Topic Vs. Change Data Capture