Saving a record into a managed environment with enough metadata and control that it can be found and relied on later. More than 'having it somewhere'; having it managed. Applies to emails and messages, not just documents.
Capturing a record is not the same as merely having a copy somewhere; it means placing it in a managed environment with enough metadata and control that others can find and rely on it. Capture applies just as much to significant emails and chat messages as to documents.
Yes. Any email or message that documents a decision, approval, or action should be captured into the approved recordkeeping system, not left in a personal mailbox or an ephemeral channel.
IAR turns terms like this into working practice: assets classified against your disposal authority, stewarded by position, and ready to evidence.