• Upper Bid Limit(Maximum Bid): The maximum amount you want to spend for a click.
• Lower Bid Limit(Minimum Bid): The minimum amount you want to spend for a click. There is a default minimum setting by the search engines. For example, minimum bid for FindWhat is $0.05, you cannot bid lower than default minimum bid.

Maximum and Minimum Bid setting in your account will be used only if you did not set up the keyword property setting for that keywords.