what is the need of Adapter Design pattern?

In the below adapter design pattern sample code, why a new class is introduced instead of using multiple interface in the client?

interface ITarget
{
  List<string> GetProducts();
}


public class VendorAdaptee
{
   public List<string> GetListOfProducts()
   {
      List<string> products = new List<string>();
      products.Add("Gaming Consoles");
      products.Add("Television");
      products.Add("Books");
      products.Add("Musical Instruments");
      return products;
   }
}


class VendorAdapter:ITarget
{
   public List<string> GetProducts()
   {
      VendorAdaptee adaptee = new VendorAdaptee();
      return adaptee.GetListOfProducts();
   }
}


class ShoppingPortalClient
{
   static void Main(string[] args)
   {
      ITarget adapter = new  VendorAdapter();
      foreach (string product in adapter.GetProducts())
      {
        Console.WriteLine(product);
      }
      Console.ReadLine();
   }
}

I have the below queries related to the above code.

• What, if ShoppingPortalClient directly inherits VendorAdaptee?
• In which scenario we need adapter class?
• why instead of simple inheritance a needed class, creating this pattern to access another class method?