Here's the difference between bidding and submitting offers:
Bidding - You can submit a starting bid and specify the
maximum amount you want to bid for a domain name. Beginning with
$5 more than the current bid amount, our Proxy Bidding Service
automatically increases your bid by $5 each time you're outbid
until you reach your maximum bid amount.
you aren't a GoDaddy Auctions member, you must purchase a
membership before you can place a bid on expired domains or
7-day auctions. For more information, see Purchasing
a GoDaddy Auctions Membership.
Submitting Offers - You can submit one offer amount per
domain name. We notify the seller immediately. The seller has
seven days to accept or counter your offer. GoDaddy Auctions
membership is not required for submitting offers.
to the complexity of conversion rates, you must enter bids/offers
currency only, even though you'll be able to view the price
in your preferred currency.
Read more on GoDaddy site.