public class MyObject { //anything can access
    public int MyInt {get;private set;} //all objects can read but only MyObject can write
    private int myInt; //only MyObject can access
    protected bool myBool; //only MyObject and objects inheriting from MyObject can access
	internal string myString; //only the current assembly can access (unless using InternalsVisibleToAttribute)
    protected internal object myObject; //any object in this assembly and objects inheriting from MyObject in other assemblies can access
	private readonly string myReadOnlyString = "hi"; //can only be assigned to in the definition or in the constructor
    protected virtual string myOverridableString {get;set;} //can be overriden in the inheritance chain
    private class MySubObject {} //only MyObject can access
    public static string MyStaticString; //access to this property is done through the type not through instances, so it is the same for all instances (hence "static") and can be thread unsafe
}

internal class MyInternalObject {} //only the current assembly can access

public sealed class MySealedClass {} //sealed means you cannot inherit from this class

public abstract class MyBaseObject {} //cannot be instantiated but can be inherited from

public partial class MyPartial {} //allows definition of class to be spread across multiple partials (e.g. for adding to auto-generated classes)

public static class MyExtensions {
    public static void ExtendedMethod(this Object o) {} //defines an extension method of the Object type
}