system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] In the films, why are so many young wizards capabale of wordless magic and what spells are any of them casting exactly?

You see a lot of magic duels in the movies of characters just throwing spells back and forth at eachother and blocking them, what spells are these?  Are they just basic attack spells? 

How much does spell speak matter in the HP-verse, you see Dumbledore and Voldemort duel eachother using seemingly complex magic without uttering a word.   So why are low level wizards in the movies able to do it?

Off question as well, in the 5th movie the aurors and Black apparate to help Harry against the death eaters but they apparate white instead of black, why?
gpt
Nonverbal spell casting is a skill that is taught in the Sixth year of Hogwarts instruction, generally in the DAtDA, Charms, and Transfiguration classes. 

If you think about the incantation as a method of getting the brain and will into the proper shape to channel the magic into the desired result, then nonverbal spell-casting is simply a sign that the magic user can achieve that mindset without needing to utilize the verbal cues. 

And the smoke thing isn't actual apparition, it's like a flair that's meant to hide other movement.