A reserve is the amount that bidding must reach before an item will be sold.  Items that have a reserve will state Reserve Not Met underneath the current bid price until that bid price has been met.  Once a reserve price has been exceeded, a notice will state Reserve Has Been Met.   Bids placed against an item that have a reserve will be consumed until the reserve price has been exceeded.

What if an item does not meet the reserve?  

Items that fail to meet the reserve are not sold and revert back to the seller.  Seller information is not provided to bidders.