Report types are a predetermined amalgamation of related objects and their fields that we can use as starting points when building new custom reports. In other words, report types are containers that contain data and fields on which we can create custom reports. The following screenshot represent a Venn diagram of outer join report type in Salesforce:
The different kinds of report types are as follows:
Standard report types
Custom report types
Standard report types are available for building reports on standard and custom objects and their related objects by default. When you are creating a new custom field, it is automatically added to standard report types. The following screenshot displays a standard report type that shows Leads with converted lead information:
