Reporting taxes

Let's say somebody buys a PS3 from my auction. They then send me a money order and I pay the wholesaler. I get to keep the profit but what do I report for taxes? What does the taxing body look at, the money order my customer sent me or do they check with wholesaler their informtion they got with me?

Keep all your Purchase records anything you buy in conducting business.
Also keep all of your payment info and your sales records. Your tax preparer will want to see these records when helping you determine profits and losses.

They look at your aggregate Profit or Loss.
If you get audited they will have a hard look at your bank statements and suppliers.