Until you are in your early 20's, drinking damages brain cells.
Now, you are 14, so drinking won't make you a blathering idiot who drools and slurs your words (although you CAN end up that when you are old if you drink too much all your life).
Instead, the brain damage you will incur from drinking before your mid-20's is subtler. It impairs your ability to control your emotions and your impulses, which means you are likely to wreck your life through unwise actions and emotional difficulties.
"Just like the body, the human brain is still developing through adolescence and early childhood, until about 24 years of age. The frontal lobe is the last part of the brain to mature, and is involved in planning, strategizing, organizing, impulse control, concentration and attention. Drinking alcohol while these changes are occurring can have negative effects on the brain’s development."
These changes can cause you to behave in ways, for the rest of your life, that screw up your attempts to get what you want, to succeed in life, career and love.