What is underscore before a variable mean?

For example

var _myVariable;


var myVariable;

I have seen some people use this convention to indicate a 'Constant', a variable that should never change.

But,technically, it doesn't mean anything.

Variable names are just identifier for the variable. The name itself has no meaning to the program or the compiler. There are a lot conventions on how you should / can name your variables. I don’t use the hungarian notation myself most likly because C# provide the type information through intelliSense ;). All i usually use is my habit (from C++) to prefix private or protected member variables with “m_”. A lot people use just “_” but some other use it for different meanings.