What Is Fasting In Islam? And What Is The Wisdom Behind It?

Ramadan is the name of the Muslims' fasting month.  Ramadan comes approximately every 11.5 months (10 to 12 days earlier every year, because the Muslim month is 29 days except for Ramadan which could be 29 or 30, and February in the normal calendar is almost always 28 days while the other months are usually 30 to 31 days such as July).  So fasting could occur during the summer and during the winter:

Narrated Anas bin Malik:  Allah's Apostle took an oath that he would abstain from his wives, and at that time his leg had been sprained (dislocated). So he stayed in the Mashruba (an attic room) of his for 29 days. Then he came down, and they (the people) said, "O Allah's Apostle! You took an oath to abstain from your wives for one month." He said, "The month is of twenty nine days."   (Translation of Sahih Bukhari, Divorce, Volume 7, Book 63, Number 212)"

The Muslims start the month of Ramadan by sighting the "new moon", which is the crescent as opposed to the full moon, and they end it by either sighting the crescent again, which would appear on either the 29th or the 30th day, or by fasting 30 days.  If the moon for any reason doesn't appear after the 30th day, then Muslims must end their fasting.

Muslims fast simply because Allah Almighty commands them to do so.  We fast from sun rise to sun set; approximately from 5:45 am till 6:00 pm.  The time range is shorter during the winter because the sun sets earlier, hence, making the fasting days shorter.  No drinking or eating is allowed during those times.