Ever pulled up to a drive-through only to find that your car window won't go down when you push the button to order. It's frustrating.
If you have electric (power) windows in your car - and most people do these days - the causes range from simple to complex. If the window won't budge if could be one of the simple causes, such as a loose connection or a blown fuse, which are easy fixes.
The reason could also be a faulty switch. If the window has been acting up, sometimes working and sometimes not, but seems to be getting worse over time, the switch is often the culprit. If, when you play with the switch, it works intermittently, that's also a clue that the contacts might be coming apart. You can try pushing if several times to get it to open temporarily. Obviously, however, you'll have to have the switch replaced.
Another reason your window may not be moving is the gaskets. Those are the rubber strips around the inside of your car's window opening that hold the glass in place. If the gaskets are worn, dirty or have debris stuck in them, they could be preventing your window from opening. You can clean the gaskets yourself and see if that helps.
There's also the issue of ice in the winter months. Especially freezing rain. When water freezes on your windows, they often freeze on the weather strip. Don't keep pushing the button, hoping it will dislodge itself. You can damage the motor this way and face a hefty repair bill. If you can't wait until your car warms up, try sliding a credit card, comb or other piece of plastic between the glass and the weather strip to break the ice holding them together.