Ebay will use the lowest amount possible to win for you - so, if you bid $200 when the max so far is $20, you might get it for $21.
But, if the person who is the high bid so far has a max that it greater - such as $50, then your bid will go to $51 and you will be the high bidder. If someone else bids with a max of $75 then your bid will go up to $76 and you will still be the high bidder.
If someone has a max bid of $250, then you will be outbid and the high bid will be $201.
When you are outbid, I believe you get an e-mail (or other form of message) to let you know you were outbid and an opportunity to bid again - assuming time allows. Lots of bidding might happen during the last minute.
So, you might want to bid your absolute max you want to pay and hope to get it for less.
Nothing wrong with bidding less (say $50) just to see what it then sets the current bid to in order to see what the previous max was. You can always bid more, or increase you max even though you are the current high bidder.
Bid with caution - no easy way to back out of a bid.
Don't bid on two or more of the same items at the same time if you only want one - you might end up winning two or more.