both...
when u click bid and you see the default value stated for your bid is the same as the current bid then it means it's the starting bid/min bid...
if higher than it means someone already bid on it...

What do you mean to ask in the 1st place?

1) When you SELL,
- the Bid price is the starting price people will begin to bid at.

2) When you are Buying/Bidding,
- the Bid price is the price you can enter to bid.
- NOTE: You can put higher Bid price of the actual current bid, and it will automatically auto-bid if someone bid higher until your Max Bid price

eg: Current Bid = 1,000
You Bid = 10,000

Someone else bids 1,100
Then system will auto raise your bid for you.
Until 10,000 max then you will fail to win and need re-bid (assuming got time)