American odds (also called "moneyline odds") are the standard in the United States. A line of +150 means a $100 bet returns $150 in profit if it wins. A line of -150 means you must risk $150 to win $100 in profit. Even money is +100 / -100.
Basics
American odds
The default US format. Positive numbers show profit on a $100 bet; negative numbers show how much you have to risk to win $100.
Example
Lakers -150 means you risk $150 to win $100. Warriors +130 means a $100 bet wins $130.