Custom settings and custom metadata are both Salesforce features that allow you to store custom configuration data. However, they have some key differences in terms of functionality and usage:

Custom Settings:
– Custom settings are customizable, persistent data objects that you can create to store data values. They are similar to custom objects and can be accessed in the same way.
– Custom settings are hierarchical, meaning you can define different values for different profiles or users. They have a built-in hierarchy structure that allows for organization and customization.
– Custom settings are generally used for storing application settings, such as feature toggles, default values, or application preferences.
– They can be accessed in Apex code using SOQL queries or by referencing them directly in formulas or validation rules.
Custom settings can be deployed and migrated across environments using change sets, packages, or Metadata API.
They provide a user interface for admins to manage the data values directly within the Salesforce setup.

Custom Metadata:
– Custom metadata is similar to custom settings in that it allows you to store custom data values. However, it is more flexible and powerful in terms of customization and usage scenarios.
– Custom metadata types are essentially custom objects that are specifically designed for metadata storage. They are meant to represent metadata configurations or definitions.
– Custom metadata is typically used for managing metadata-driven functionality, such as dynamic business rules, configuration settings, or application metadata.
– Custom metadata supports field types that are not available in custom settings, such as picklist fields or relationship fields.
– Custom metadata records are treated as metadata rather than data, meaning they can be deployed and managed using Metadata API, including tools like change sets and packages.
– Custom metadata records are read-only in most cases, meaning they can be accessed but not modified at runtime. Changes to custom metadata require a metadata deployment process.
– Custom metadata provides a powerful way to build customizable, metadata-driven applications that can be easily extended and configured by admins without code changes.

Conclusion
In summary, custom settings are primarily used for storing application settings and are customizable at runtime, while custom metadata is more focused on managing metadata-driven configurations and is typically deployed as part of a metadata deployment process. The choice between custom settings and custom metadata depends on your specific requirements and the nature of the data you need to store.