A number system defines how we represent numbers. It defines which digits we can use, and what value each position (place value) in a number has.
The number base of a number system defines how many digits are in the number system, and the base of the exponent for each place value in a number.
The number system we use in out everyday lives. It has 10 digits, 0-9.
Number system that has 2 digits, 0 and 1. This is how computers represent numbers at the base level.