The active version of an ABAP Dictionary object is the one that is accessed by the components of the runtime environment, such as the ABAP processor and database interface.
On the other hand, the inactive version is created when an active object is changed. It does not affect the runtime system. The inactive version can be changed into an active version through a process called activation.
The slide here illustrates change in the status of an object. Initially, an active structure contains three fields. When an additional field is added to this structure in the ABAP Dictionary, it results in two versions of the same structure. One is an active version containing the original fields and the other is an inactive version containing the additional field. During the activation process, the inactive version replaces the active version. Thus, the inactive version becomes the active version resulting in only a single active version with the four fields.