What is vendor reconciliation.

Yes,vendor reco is definitely accounts related job.Its part of accounts payable activity where one has to reconcile vendor balance in his books of accounts with that of the vendor balance in the books of the vendor.
Take a statement of account from the vendor
The statement must have invoice wise detail of each transaction.
Compare the statement with the vendor accounts as per your book.
Any difference should be separately shown in the reconciliation statement.

Sample reconciliation statement:
Balance as per ABC(Vendor) Statement:
Less: Payment not reflected in vendor a/c
Less:Invoices not booked by us
Add:Invoices booked by us but not reflected by vendor
Balance as per our books of accounts