The following five accessibility levels can be specified using the access modifiers:
public: Access is not restricted.
protected: Access is limited to the containing class or types derived from the containing class.
Internal: Access is limited to the current assembly.
protected internal: Access is limited to the current assembly or types derived from the containing class.
private: Access is limited to the containing type.More Info : http://msdn.microsoft.com/en-us/library/wxh6fsc7(VS.80).aspx