There are 2 purposes of explicit implementation of Interface:
First, it is used to avoid name collision between interface methods. That is if you are going to create a class library, there may be a chance to use the same name in several places. At that time "explicit" implementation comes as a rescue.
Secondly, You cannot access that implemented method through the object of the class directly. Instead you typecast it as Interface reference then you can access it. This is because, the C# complier, unable to determine which one the user want to call.