A straight bid is a one-time amount, that represents the price you are committing to bid. The price that is entered as a straight bid can be any amount that is equal to, or greater than the current amount plus the minimum increment.
This amount will become the new current bid amount of the item (i.e. the item is $100. A straight bid is placed at $200. The item price is now $200).
If there is a maximum bid on the item, the greater of the straight bid and maximum bid will be the highest bid amount.
If a straight bid and a maximum bid are placed at the same value, the bid that is placed earlier will become the winning bid.