If you've played golf for more than a hot second, you probably know of lakes and streams and rivers and oceans on a golf course as "water hazards." There are different types of water hazards, yes -- there are regular water hazards with yellow stakes and lateral water hazards with red stakes.
Under the new golf rules in 2019, however, you'll start to hear golfers and golf commentators on TV start to refer to water hazards by a new name. In the 2019 Rules of Golf, water hazards are now known as "penalty areas."
What are penalty areas?
The USGA and R&A decided to create the idea of "penalty areas" as a catch-all term to include water hazards, yes, but also other portions of the golf course which, under the new Rules of Golf, can be marked as a red- or yellow-stake hazard. The new golf rules allow courses and tournament operators to mark areas like forest, jungle, desert, lava rocks and more as a "penalty area."
Why make the change?
This change was made to give these tournament operators and courses the flexibility to declare portions of their courses as a hazard. Under the new Rules of Golf, golfers are allowed to ground their club in a hazard, er, penalty area. The USGA and R&A realized needing a hazard to have water in it as a requirement was arbitrary and inflexible.
So, by giving golf courses the option to declare more parts of their property as penalty areas, they give golfers more options. A golfer can choose to take advantage of a certain marked area of a course being a "penalty area" by dropping out of them within two club lengths if they're a lateral penalty area or by replaying the shot with a one-stroke penalty from the original position if in a regular "penalty area."
The USGA hopes this will mean golfers don't chase their golf balls into areas they shouldn't be hitting, in desperate search of a ball that they won't be pleased to find and play. Instead, they can declare a ball in a penalty area, take a penalty and move on with the round.