Just to add to what others have said - this shouldnt be done only in the winter. If you have a car that your not currently driving you should idealy start it once a day year round, regardless of the weather. Let it run for about ten minutes. This helps with numerous parts because it gets fluids, oils, water, gas, and your battery all moving and working so that its not all sitting. If you dont start up your car enough your risking numerous problems.
In winter you must have to start your car once a week other wise it may cause problems in her engine. Starting a car Once a day is ideal. It helps to keep the parts of the engine lubricated which is really essential. Also before driving the car wait for atleast 5 minutes to let the engine become hot. Not only starting the engine try driving the car for atleast half an hour without stopping it.
If your storing your car for an extended period of time ( 3+ months ) i spray an engine spray in the intake (brand name like engine-stor) and remove the battery. I then charge the battery once a month for an hour or two.
but if its only for a few weeks i start the car every couple of days for about 5 or 10 mins. ideally take it for a 10 min drive or so
I generally start it once a day and let it run for 10 minutes if I won't be driving at all that day. In the winter, I also tend to let the car warm up for 3 minutes before starting to drive.
To keep it charged you'll need to drive it a bit