The tip fizzes, producing bubbles.

"Hmm, yes, I see. Try this one. Pine, dragon heartstring, ten inches, slightly brittle." 

He tries yet another one, "phoenix feather, yielding, black walnut".

This one at least produces something, a puff of gray smoke. 

Bubbles aren't fun. He tries the new one.

It feels warm in his hand, but nothing else happens.

"Hmm, yes, it likes you, but not the best we can do."

He snatches it back.

Scott attempts again, with a "whippy rowan, dragon heartstring".

The wand practically wilts as he holds it.

"What's the difference between the wands?"

"I'm afraid a true study of wandlore takes a lifetime. What in particular were you asking for?" 

He hands Sadde another one, "pine, 9 3/4, dragon heartstring".

"What the cores and sizes and woods do and how you know a wand is good for us and how you look for new wands once you decide one's not good."

Wave.

And there's an explosion.

Not a destructive, uncontrolled one; a show of lights, purely visual but very pretty and with a strong fire theme.

Scott...still doesn't have a wand. 

"If you're waiting for this boy to find his wand, we can certainly cover some of that. Assuming you're satisfied with this match?"

"Yes! I want it! And I'll wait for him."

"If your mother can pay for the wand, I'll accept that for a brief lesson."

Payment: happens.

Sadde: watches.

"Very well. Enjoy the wand, boy. Now, for your lesson. Wood and core reflect a wizard's character, augmenting it. Some wands seek wizards to balance, while others seek witches that match. Wand length is often based on the size of a wielder's personality, and flexibility represents their flexibility, if you will. Take your wand. Smaller than average, but not unusually so. You are more restrained in your expression of your core traits- but as we take a look at the wood and the core, we'll see your flashy tendencies are reflected elsewhere."

"Huh. So... Scott should probably get something nice and kind that likes helping others, from what I've seen?"

"I'm sure that's right, though I don't know the boy at all. I typically get a sense by offering a more friendly, adaptable wand first, to see why it doesn't fit, if it doesn't, and move on to a more suitable fit." 

Pear, unicorn hair, slightly bendy?

Nope. 

"Don't people change a lot in their teens, though?"

"Some will find new wands as they get older, if not wiser. Most pairs, however, will grow together. The wand chooses the wizard." 

"—are wands sapient, too?"

"I'm not quite sure what you mean."

Cedar, dragon heartstring, eleven inches...

It gives off a few sparks, which Scott seems pleased by, but Ollivander shakes his head and retrieves another one.

"Are wands people? Do they have memories, personalities, thoughts, preferences?"

"I can't say I've ever wondered if wands had memories, but they do have temperaments and preferences. They may be no more complex than Crups or Granians, but they are unique."