This sounds like your battery is low. With a 2001 vehicle, it is possible that the battery needs to be replaced; they usually do after 3-6 years. It is also possible that the alternator is going bad and not charging the battery. You could have left a light on inside the vehicle, and that ran the battery down. The battery terminals could be dirty, or lose, and not be making good contact. The starter could be going bad, and drawing too much power from the battery. If you are trying to fix this yourself before taking it to a qualified mechanic, try the following, in order.Check the battery terminal connections, make sure they are tight. Loosen the battery terminals, and clean them, using either fine emery paper or a wire bush. Clean the posts on the battery the same way. Replace and tighten the terminal connections.If it is not a sealed battery, check and fill the water level.If the car still does not start, either charge the battery, or try a jump start. If the car starts with a charged battery, take the car and have the battery load tested. This should be very inexpensive, most places will do it free to try to sell a battery. If the battery is weak, have it replaced.If the car will not crank with a jump, it is most likely the starter, and the car will have to be towed, (unless it is a manual transmission that you can push start) to a shop for repair.