What is the difference between the Implicit and Explicit Calling?

Question

Hi all,
 
Can any one tell me what is the difference between the explicit and implicit calling of a method?
Like when we put cursor and press ?Alt+Shift+F10 on the Interface we will be able to see the two options.See this example
class TestInterface : IFirst, ISecond { static void Main(string[] args) {   } }W