Explanation of naming conventions for classes, methods and variables

I'm currently in University and they're pretty particular about following their standards. They've told me this: All classes must start with a capital letter Correct ``` public class MyClass {} ``` Incorrect ``` public class myClass {} public class _myClass {} ``` All methods must start with a lowercase letter Correct ``` public void doSomething() {} ``` Incorrect ``` public void DoSomething() {} public void _doSomething() {} ``` all variables must start with a lowercase letter Correct ``` string myString; ``` Incorrect ``` string MyString; string _myString; ``` Yet in my last year of programming, I've been finding that people are using much different rules. It wouldn't matter if it were just a few people using the different rules, but almost everywhere I see these different practices being used. So I just wanted to know what the reasoning behind the above standards is and why some of these other standards are being used: (are they wrong/old standards?) Most methods I've seen start with a capital letter rather than a lowercase-- Pretty much any of Microsoft's methods I've been using from their imported namespaces. This is probably the most common one I've seen that I don't understand A lot of people use _ for class variables. I've seen capitals on variables ie. `string MyString;` I know I've missed a few as well, if you can think of any that you could add in and give an explanation for that would be helpful. I know everyone develops their own coding styles, but many of these practices have reasons behind them and I would rather stick with what makes the most sense. Thanks, Matt