Explain the differences and use cases between record types, page layouts, and permission sets in controlling access to fields and layouts on a specific object?

Record types, page layouts, and permission sets are all fundamental tools in Salesforce for customizing the user experience and controlling access to fields and layouts on a specific object, but they each serve distinct purposes and have unique use cases. Record types are used to offer different business processes, picklist values, and page layouts to different user groups based on the nature of a record. For example, if you have a custom object for 'Cases,' you might use record types to differentiate between 'Technical Support Cases' and 'Billing Support Cases.' Each record type can have its own set of picklist values, allowing you to offer appropriate choices depending on the type of case. Users can be assigned to one or more record types which can limit the data entry and viewable data depending on their selection. Each record type can then be associated with specific page layouts.

Page layouts, on the other hand, are used to control the organization, display, and behavior of fields, sections, and related lists on a record page. They dictate what fields are visible, required, read-only, or editable for users when they are working with a record. A page layout is always tied to a record type. If a user has access to multiple record types, each record type might have a different page layout. For instance, for 'Technical Support Cases,' you might have a page layout that includes fields related to software versions and server details, while 'Billing Support Cases' might have a layout with fields for billing addresses and account numbers. Page layouts also allow you to define how related lists are displayed and which buttons and actions are available on a record page. This means that the same object can display different information based on the page layout assigned to a user, ensuring that they are only viewing relevant information. Page layouts enhance user efficiency by providing a context-specific interface.

Permission sets are used to grant additional permissions and access to users, beyond what their assigned profile provides. Permission sets are not tied to record types or page layouts directly. Instead, they grant users access at the feature and field levels. Permission sets can grant a user access to specific fields on an object or grant feature licenses. If a profile allows read access but a permission set can grant write access to the same field or grant additional access such as 'Modify All'. A user’s permission access is based on the profile and any permission sets assigned to them, resulting in a cumulative set of permissions. Unlike profiles that are typically defined per user role, permission sets can be more targeted and can be given to individual users across different roles based on their need. For example, a user with a profile that does not allow access to specific sensitive fields can be granted access using a permission set that grants 'Modify All' to a custom object or read and write access to sensitive fields. Permission sets can also include system permissions, app permissions, or tab visibility.

In summary, record types control the business process and data entry options, page layouts control the display and layout of fields on a record, and permission sets control the ability to access and perform specific actions on fields and features. A record type allows different page layouts and picklist values to be assigned depending on the type of record, while page layouts control the arrangement of fields and user actions, and permission sets determine the feature access and ability to access and edit specific fields beyond the profile permissions. In practice, you would use them together to create a tailored experience for different users. For example, a sales user might use a specific record type with a simplified page layout that shows only the most critical fields, while a sales manager using the same object might have access to a different record type with a page layout that displays all the fields, and a specific permission set that grants them more access to data, and features that users in the sales role do not have access to.