|"Is this all real? Or has this been happening inside my head?"
The topic of this article is of a real-life subject that has been mentioned "in-universe" in a canon source. The Harry Potter Wiki is written from the perspective that all information presented in canon is true (e.g., Hogwarts really existed), and, as such, details contained in this article may differ from real world facts.
Chestnut (genus Castanea), some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae
According to Garrick Ollivander: "This is a most curious, multi-faceted wood, which varies greatly in its character depending on the wand core, and takes a great deal of colour from the personality that possesses it. The wand of chestnut is attracted to witches and wizards who are skilled tamers of magical beasts, those who possess great gifts in Herbology, and those who are natural fliers.
However, when paired with dragon heartstring, it may find their best match among those who are overfond of luxury and material things, and less scrupulous than they should be about how they are obtained. Conversely, three successive heads of the Wizengamot have possessed chestnut and unicorn wands, for this combination shows a predilection for those concerned with all manner of justice."