Trespassing isn't always clearly defined. Trespassing can occur in any number of circumstances. The charge usually follows under four different categories. Trespassing on property means you willfully entered property without being authorized, or licensed, or invited. When you are caught trespassing on school grounds, it means you didn't have any legitimate reason to be on school property. "Trespass in a structure" has an odd ring to it, but it basically means you had no right entering a building of any kind. Think of a house being built. Finally, there is trespassing in a conveyance. A conveyance is any motor vehicle, ship, vessel, railroad vehicle or car, trailer, aircraft, or sleeping car.
Take a wrong turn? Walk in the wrong backyard? Sometimes we just step into a bad situation. Trespassing occurs when someone sets foot onto someone else's land, home, car, etc. Basically entering a property that the owner didn't give you permission to enter. A very common example of a "trespass charge" is when a person enters a bar or a nightclub after being refused entry by a bouncer or security guard.