Is early decision really binding, or can I still get out of it?
The answer is it's both. Yes, it's really binding. You, your college counselor, and your parents will all sign a piece of paper indicating that you understand the binding nature of the commitment you are making and that you will attend if admitted.
That said, nobody is going to show up at your house with a pair of handcuffs if something happens and you are unable to to attend. Notice I use the word 'unable.' That's different from, "I changed my mind and would rather go someplace else."
'Unable' means there's been a significant change in your situation in a way that affects either your ability to pay for school or your ability to physically be present on campus. Perhaps a financial aid package with the institution didn't work out, or maybe a parent has passed away or a family business has gone under. If any of those things happen, make sure to speak with someone in the financial aid department before deciding it's impossible to attend. Or perhaps you've had a serious health issue or accident. If that happens, look into taking a gap year - postponing your enrollment at your school - before deciding it's impossible to attend.
An early decision agreement is serious. You should make every effort to adhere to the commitment you agree to when you apply.