Verb second is the phenomenon in which the finite verb is preceded by exactly one constituent. Not all languages have verb second, though, as can be seen here. The only thing I do not understand is why a simple clause with a SV order is not considered verb second.
As an example.
[The man] bites the dog.
The verb is clearly in second place here. So why isn't this called verb second? Is it because verb second has to involve verb movement? Or because the first element should not be the subject?
I am puzzled, mostly, because some authors argue - correctly, I believe - that English is not strictly speaking a V2 language. What confuses me about that, is that the most basic sentence in English (as the example given) does have a V2 word order, and also in subordinate clauses English seems to hold a V2 word order.
He said that the dog [had bitten] him.
In contrast with Dutch:
Hij zei dat de hond hem [gebeten had].