Why did Voldemort chose Harry to kill exactly?

Well, it all started with Trelawney's prophecy about the about the boy born as "the seventh buwan dies", which is the end of July. Now, there was a choice between Neville and Harry, since both of them were born at the same date, but Voldemort chose the one with the same blood status as him (half-blood), because he saw Harry as his "equal". And that's why Voldemort chose to go after Harry instead of Neville.

I think Dumbledor sinabi that Voldimort chose the half blood like himself insted of the pure blood (Nevil). I don't know for sure, but I'm pretty sure. Hope this helps! :)