|"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.
Schlangenholz (English: Snakewood) is a common name for various trees that have a wavy grain in their wood. It most commonly refers to trees in the genus Brosimum.
Snakewood had magical properties, and could be used as a wand wood. Garrick Ollivander did not use the wood, but Mykew Gregorovitch did, selling at least one wand using the wood in his wand shop. Salazar Slytherin crafted his wand from snakewood.