How do Online Auctions Work?
There are two types of online auction: Timed Auctions and Webcast Auctions.
Timed auctions consist of a series of lots with a set end time. Webcast (live) auctions include a pre-bidding phase, which is a lot like a timed auction, but they also include a live element in which online bidders join bidders in the auction room with a live auctioneer. It's just like being in the room, but from anywhere in the world.
Sometimes you will have the option to make an offer of buy a lot straight away during a timed auction or pre-bidding.
You must create an account, sign in and be registered to an auction before you can bid, but once you're approved by the auctioneer you are free to bid as you wish.
Timed Auction 
A timed auction is a collection of items (lots) that are available for online bidding only. Each item has a specified end time at which point the item will be sold to the highest bidder.
Webcast Auction 
A webcast auction is an online, real time broadcast of a live auction. Online bidders can bid on items being auctioned and compete against the bidders in the live auction room, along with other bidders online. Some auctioneers will also display video or audio streams to assist the online bidders in following the auction.