The first result is that every bank and credit-card account reconciles — its ending balance in QuickBooks matches the statement, with no unexplained difference and no pile of stale uncleared items.
Reconciliation is the load-bearing result because everything else depends on it. When an account ties to its statement, you know every transaction that should be there is there, nothing is duplicated, and nothing was invented. That is what turns a profit and loss from a guess into a report you can act on. A finished file has each account reconciled through the agreed period, the uncleared list explained rather than ignored, and any opening-balance oddity resolved instead of buried. You do not have to take that on faith: a reconciliation is the one result you can re-run yourself, statement in hand, and confirm to the penny.