I began practicing mindfulness about 10 years ago when I was a teenager (probably around your age, from the sound of it) and it has helped me tremendously. Mindfulness is like a higher state of awareness; it's thoughts about your thoughts, being aware of your awareness, etc. It allows you to take a mental step back and see yourself from an almost unbiased point of view, as if you're looking in on your mind from somewhere else, watching your own thoughts and emotions as if from a higher vantage point.

It's a huge topic, but the easiest way to begin is to simply sit back, relax, close your eyes, and focus completely and entirely on your breathing.

If you have some time to kill, here are two really great videos about mindfulness which will help you get started:

https://www.youtube.com/watch?v=5TeWvf-nfpA This video is a panel of doctors and neurologists talking about how mindfulness is good for you and why it helps you, physically, emotionally, and mentally. I would recommend watching it first, but it's not entirely necessary.

https://www.youtube.com/watch?v=3nwwKbM_vJc This video is a man named Jon Kabat-Zinn explaining what it actually is and, in the second half of the video, giving you a chance to try it yourself by guiding you through it. Guided meditation sessions, particularly well done ones like this, are very easy to follow and give you a great starting point to build your own experience off of, or even expand your existing knowledge, for those who have been meditating for a while already. You should definitely watch this video in its entirety, and try to do so when you know you won't be disturbed through the second half, the guided meditation.

Feel free to reply or send me a PM if you have questions, I love seeing the idea of mindfulness spread and would be happy to help.