Final answer:
The revision block or revision table on a P&ID indicates changes made to a plant area. It includes details like the change description, date, who made it, and the revision number. This section is vital for keeping accurate modification records.
Step-by-step explanation:
The section of a P&ID (Piping and Instrumentation Diagram) that tells what changes have been made to a plant area is known as the revision block or revision table. This section is essential for maintaining accurate records of modifications over the life of the plant. Every time a change is made to the P&ID, the details of the change are noted in the revision block. This may include information such as the description of the change, the date it was made, who made the modification, and the revision number. The revision block acts as a historical record, ensuring that all stakeholders have a clear understanding of the current state of the plant's design.