Believe me you'll know the difference. I remember with my first pregnancy I was worried I wouldn't know....I knew alright. It'll be a pain you haven't experienced before and it will keep getting worse and closer together.
Braxton Hicks is really dull & uncomfortable. Real labor is really painful and you'll know the difference. Drink water and lay down, it helps with the braxton. When you go into real labor nothing will help ease the pain and it'll be constant and become worse over time.
Contractions are actually painful. They say BH can be painful but mine never were. I didn't know what the contractions felt like until I actually had them the day I went into labor. Some women describe them as period like cramps that get stronger and worse. I've never had period cramps so that didn't help. It started out feeling like pressure in my vagina - I honestly kept feeling like I had to pee but you can only pee so much! It progressed into feeling like someone was pushing outwards from the inside of my vagina. Then the contractions got longer and actually painful. As frustrating as it may sound, you'll just know when you're having real contractions. It's so hard to describe how it feels.
Bh can be as painful as real contractions at least that what mine were. I believe the difference is whether or not you are progressing. Like the contractions getting more regular and closer together, becoming more dilated. I hope this helped.