As you slide down the plastic slide, electrons move from the plastic to you. Now you have extra electrons. Touch another person or an object (anything that isn't negatively charged by extra electrons) and ZAP! The electrons move from you to the other object. You get a shock. This is called static electricity ( more correctly called "net electric charge" ). It appears whenever the normal quantities of positive and negative electricity in a substance are not perfectly equal.

Remember that everything is made of atoms, and atoms in turn are made of positive and negative electric charges. In other words, your body is just a collection of positive and negative electrical particles. Normally the positives cancel out the negatives, and everything behaves electrically "neutral." No mysterious sparking. But if you ever end up with more negative than positive, or with more positive than negative, then you have a charge-imbalance on your body. You will get zapped the next time you touch a large metal object.