People like you and me that love to have a dance and a laugh in a field. People that have a drink and become friendlier, that migh laugh and giggle, hug you and fall over.
They may fall onto your tent at 1am and spend 35 noisy minutes apologising.
People at festivals are the best people.
But like anywhere in life there are some exceptions, there are some twats, there are some people that can't hold their drink or become nasty on it. There are people that do illegal drugs, that like a fight...there are even ...thieves.
So take a few precautions and stay safe. I tend to expect the best but plan for the worst. Don't keep all your money/cards etc in one place. If there are a few of you in group ensure you all carry some of the valuables. Maybe leave an emergency fund hidden in the car? Don't leave valuables in your tent. This includes cash, cards, electronic games and phones. At night put your cash and phones etc into the bottom of your sleeping bag.
Keep your bags etc with you. If you snooze on a picnic run ensure your valuables are not just laying around or in a bag nearby, use a bag as a pillow, or keep stuff on you.
Try not to get too drunk. Tipsy or tiddly is nice, falling over puking drunk is not, and you are more likely to drop and lose important things like car keys or phones.
Be nice to other people and assume they will be nice back, If you see or suspect trouble let the security team know, don't try and deal with it yourself.
Camp Bestival (and most festivals) have a great security team, also handy for radioing around and finding lost kids..
Have fun, Stay safe.