What does it mean to assign a variable as 'false'?

a = false ; 

is this somekind of a state variable which controlls 
function's behaviour  or something like that ????
i googled it and i didn't find any  answer ???

Look at this and this.
It just a value type for variable. Like var num=1; for number or var str = β€œblah” for string. booleans are just another type. Imagine a function that return false if one set of condition is met or true if another one is met. And that result is delivered to variable β€˜a’ …