What is the difference between a buy order and a normal bid?

This is a one-time bid. If you are outbid, you must bid yourself.

You set a maximum price that you are willing to pay for a lot. The system will then automatically bid on behalf of the buyer up to this limit, but only the minimum amount required to be the highest bidder. This may mean that the winning bid is lower than the specified limit.

Other buyers cannot see which buy order you have entered.

The maximum price of the buy order always has priority over a normal bid that is equal to the maximum price of that buy order.

Example:

A buy order is set up to 1000€.

A pigeon is at 950€ and you bid 1000€. Your bid will not be effective because the buy order has priority.