Closeout documents include warranties, operation and maintenance manuals, as-built drawings, attic stock and training records. Division 01 and each spec section list what is required.
Example: a gym equipment section requires owner training on the motorized backstops and a set of maintenance manuals.
Closeout costs money, so read those requirements at bid time. Count the training hours, extra material and return trips. Put that cost in your bid. Final payment and retainage often wait on closeout. A late manual can hold up a large payment.