Packages in Delphi - ablealias/Delphi GitHub Wiki

A packages are special dynamic-link library used by Delphi applications, the Delphi IDE, or both. Packages enable us to place portions of our application into separate modules that can be shared across multiple applications. Packages, also, provide a means of installing (custom) components into Delphi's VCL pallete. Therefore, basically two types of packages can be made by Delphi:

• Run-time packages - provide functionality when a user runs an application - they operate much like standard DLLs.
• Design-time packages - used to install components in the Delphi IDE and to create special property editors for custom components.