There are many kinds of Engineering. But it's not like pure science. Engineers are involved in designing everyday things that make our civilization possible. It can range from a small thing, like a computer/radio chip that might lurk inside a power meter on the side of your house. It can also be very large things like an offshore wind farm.
Engineers study existing designs and innovate. There is an art to the designs that very few will notice, let alone appreciate. However, Engineers are not usually involved in discovery. That's the realm of the Scientist, and the Physicist in particular. If you are enamored with the idea of discovering things that have never been known before, then consider a career as a scientist.
Scientific investigations are almost never lucrative for the scientists. By comparison, though Engineers rarely get rich, they have historically received middle to upper middle class salaries. I should caution you that although the earnings history is a fact, predictions are often wildly inaccurate. What has happened in the past is no guarantee that this will be what you get if or when you graduate.
As for kinds of engineering, there are many applications and kinds of engineering. The broad swaths are Civil, Electrical, Mechanical, and Chemical Engineering. There are also corrosion control engineers, Software Engineers (for embedded software), Aeronautical Engineers, Control Systems Engineers, Marine Engineers, Environmental Engineers, Industrial Engineers and so many more.
Consider what you like doing. Do you like building construction sites? Do you like industrial plant sites? Have you ever really been to any of these sorts of places? Think about whether you'd like to travel or whether you prefer routine office work. Do you like getting involved with your work or would you prefer to stay at arms length? Engineering can be all of those things.
I find that while I think the work is interesting, it's the people I work with that make it enjoyable and worth doing. At age 15, you still have much to learn about what work places are like. Don't make up your mind yet, but think about broad goals of what you'd like to see yourself doing. Be on the lookout for every opportunity you can get to learn about various professions.
If you had told me when I was 15 years old that I would be working at a water and sewer utility, and finding it enjoyable, I'd have been horrified. And yet, here I am.
I design industrial control systems and wide area SCADA (Telemetry) systems. I deal with energies and scales of operation that very few people comprehend. It's truly awesome seeing the systems I designed, programmed, and tested operate extremely large infrastructure that millions depend on. I also have a very broad cross section of people to work with, from misfits who didn't even graduate from high school, to very smart thought leaders of industry, to political hacks of all persuasions, to managers and bureaucrats ranging from churlish to genuinely helpful and understanding. I get to work with them all. And the work matters. Without the things our company does, our cities would be unlivable in just a few days.
Get involved in various hobbies and engineering clubs in school. Look into interests such as Amateur "Ham" Radio, home chemistry experiments, software design, Robotics, automobile repair, rocketry, or even your local marina or airport. People are usually happy to share their experience and opportunities with you. Don't wait for these people to come to you in your school.
Good Luck!
