First off we have to understand what a variable is.
A variable is a storage location that you can use to declare a data type and assign that data type a corresponding value. This means that if you plan to use a reference to something repeatedly, you can just name that value and declare it as a variable to be called upon throughout your script(s).
So what makes up a variable?
Variables consist of 4 parts: The Reference, Data Type, Name, and Value. The fourth one (Value), doesn’t have to be declared in your script and is thus “optional”. Every variable has a default value though.
“Public” variables are visible to other scripts and “Private” variables are not.
“Int” stands for “Integer” and represents a whole number.
“Float” represents a number that may contain a decimal value.
“Bool” stands for “Boolean” and is a true or false value.
“String” is a line of text or (a string of characters).
It is not good practice to directly change variables from other scripts as it can bog down your program. To do this properly you should call a separate method from within the script that contains the variable and change it in there.