There are all types of auctions, including farm auctions and real estate auctions, but livestock auctions are a different breed of animal, pardon the pun. Auctioneers still try to get the best prices for sellers. And your adrenalin can start running quickly in the environment created by auctioneer's cadence and the ringmen's "Yep!"
If you're not sure how to handle yourself at a livestock auction, take a couple minutes to read How Not to Act in the Sale Barn. The article includes lots of great tips and a good overview of the process.
One additional thing to consider: Critters can pick up diseases in sale barns, so be careful to buy only healthy animals and minimize stress for them.