Bidding for your auction will start at this price.
The opening price is the lowest price at which you are willing to sell your item (unless you also specify a reserve price). Bidding will start at this price.

Tip: Sellers have found that setting the opening price too high may discourage bidding.

If you are using the Instant Purchase format, you'll enter a Fix Price in the same field (opening price), simply enter the price at which you wish to sell your item or items.