The period symbol is used in math to represent numbers using the decimal system. Typically, the symbol is used in an expression like this to represent a number:
In plain language this is read as the number “six point two eight three”. Read more here.
The decimal point is used to separate the whole part of a number from the decimal part. The whole part is represented using number digits to the left of the decimal point. The decimal part is also represented using digits to the right of the decimal point.