Timed auctions
A timed auction is an online catalog you bid through at your own pace. Every biddable lot has its own published closing time. Where max bidding is offered, a confidential maximum lets the system compete for you within your limit. There's no scheduled ring to attend.
Webcast auctions
A webcast auction takes place at a scheduled time. At the start time a clerk works through the catalog in real time and you bid online alongside the floor. You can also leave a prebid ahead of the auction so you stay in contention if you can't watch the moment your lot comes up.
Listing-only catalogs
A listing-only catalog is there to preview. It shows lots, photos, and details so you can plan, but it isn't open for bidding. If an auction you're watching is listing-only, check back — the auction company decides if and when a biddable auction follows.