The Salesforce platform provides some predefined standard report types that involve diverse objects and conditions (which cannot be modified) and a huge list of custom prebuilt custom report types that are free to use.
An exhaustive list of built-in report types can be found at https://help.salesforce.com/articleView?id=reports_report_type_reference.htm&type=5.
To create a new report type, go to Setup | Features Settings | Analytics | Reports & Dashboards | Report Types. A quick how-to guide is shown on the main report type page, that is, if you haven't hidden it yet.
Click the New Custom Report Type button and select the Primary Object, which is the main object the report type refers to.
Remember the following key points:
