What does truncating a custom object do in Salesforce?

Truncating a custom object in Salesforce refers to the process of permanently removing all records from that object. This action clears all the data stored within the records of the custom object while retaining the object's metadata, such as fields, relationships, and configuration settings. Therefore, all of the records will be deleted without the possibility of recovery, making this choice accurate.

The other options do not accurately describe the truncation process. For instance, truncating an object does not involve deleting the object itself or its related metadata, which is crucial for understanding the overall structure and functionality of the custom object. Additionally, truncating does not discriminate between active and inactive records, nor does it affect the object's fundamental purpose or functionality—it simply clears out the data.