A variable is a way of storing a number or some text.
Every variable must start with a letter [a-z,A-Z] or the underscore character followed by letters, numbers and underscores up to 31 characters.
Variables are case sensitive, which means a & A are different variables. If a
variable name ends with a "$" character, it holds text,
otherwise it holds a numeric value.

With Rounding mode on (default) the smallest number you can store in a variable is 0.000000000001

Rounding keeps numbers accurate to 12 decimal places to the right of the decimal point.

When numeric values exceed 999999999999999 they are stored in an exponential form which looses precision. Above 999999999999999 answers will only be approximations.

Big Decimal string arithmetic is provided for calculations that require absolute accuracy with any size decimal number.