Once a bank account is connected, transactions flow into Xero's Reconcile tab automatically. For each line, Xero suggests a match, usually an existing invoice or bill it thinks corresponds to that amount, or offers to create a new transaction and asks you to pick the account and tax rate. Confirming a correct suggested match takes one click; everything else takes a few more.
Reconciliation rules let you automate the repetitive cases: a recurring bank fee, a regular rent payment, a known monthly subscription charge. Set the rule once with the matching criteria and the coding it should apply, and Xero handles that line automatically every time it shows up, rather than asking you to code the same transaction by hand every month.
For bulk situations, like reconciling a batch of similar small transactions at once, Xero supports matching multiple lines in a single action rather than clicking through them one at a time, which helps but still depends on someone noticing the batch and running it.