Binary and the Bit. The decimal number system has ten numbers available. Since there are ten numbers available, then it's base is ten. However it's not the only useful Number System. In computing there are four useful number systems.
Position plays an important role in determining the value of a number in any system.
For example, consider the decimal number 932. There are three digits. That on the right represents the least value. The digit on the left has the most value. Looking from the right then the whole number has the following total value.