"If Not 'someCondition' Else" Logic

I have a few co-workers who implement if-else logic in a way I've not seen before, and it kind of baffles me.

They write...

If <someCondition> Then
Else
    Console.WriteLine("Hello, World")

...instead of

If Not <someCondition> Then
    Console.WriteLine("Hello, World")

This got me thinking

Is there any difference between the two approaches? Is one approach more efficient than the other?