Knowing the mechanics of what makes your toilet work will help if your toilet breaks down. Sometimes, however, the only option is the professdional plumbers in NYC. Most people do not know what the things in the tank behind the bowl do. Although most toilets are different they still mostly function on the same principles. If you flush the toilet with the top of the tank off then you can see how everything works.
When you press the flusher down it lifts up a chain connected to a flapper. This allows for water to go from the tank into your bowl. You will also see a balloon like object that drops as the water drains. The float is connected to a valve, which regulates how much water goes into the tank (so it doesn't over flow). Knowing these few basics could potential save you a lot of time and money.
After you flush your toilet you hear the sound of running water, and that is because the back tank is filling up with water. If that running sound does not stop then you should take off the top of the tank. A lot of times the problem is as simple as pushing the flap down. It could just have gotten dislodged or maybe the chain got caught somehow. If you open up the tank and you can't see why the water is still running then it is time to call a professional. Your toilet might constantly run because you don't have enough water to deactivate the float. Once your tank hits a certain amount of water then it will shut off, but if it doesn't get there then it won't shut off. You can check the water valve on the wall to see if the water is up all the way. Another reason for the issue could be a loose stopper.
There are certain things you can do for yourself and your bathroom that is a quick and easy fix, but please do not think that all plumbing jobs are simple. If you can see an obvious problem then you should try and fix it (if you can), but if you can't see the problem then you shouldn't start to tinker. Tinkering usually only leads to making a problem worse. There is a reason there are professional plumbers in NYC, and that reason is because they are trained to fix your bathrooms and toilets.