Wood
"A portable bundle of wood. You can use this to make a campfire if you have something to light it."
Wood is a material found in Breath of the Wild. They can be obtained by felling trees and cutting them up with a weapon such as the Woodcutter's Axe or a Sword, but, pre-cut bundles can sometimes be found at the many Stables found around Hyrule. Wood can be used to start a campfire if Link by using a flame based weapon, a lit torch, a Fire Arrow, or a Bomb Arrow. Alternatively, Link can strike Flint with a metallic weapon causing the wood to light on fire. However, Link cannot set a campfire while it is raining.
Gathering Wood
Almost any large tree in the Overworld can be cut down using a sword or an axe. After a tree is knocked know, one more slash will cause a bundle of wood to appear. Alternatively, Link can use a Bomb to knock down trees and a second bomb to blow up the timber, causing wood bundles to appear without having to use weapons.
At the Rito Stable, there are a number of large wood logs behind the stable and in the nearby forest. Along the path leading south, there are an abundance of trees and it is a great way to farm wood.
Another good place to farm wood is in the forest area just east of the Satori Mountain. Just north of a small pond, there is an abundance of Apple trees that are all close to each other. In a short amount of time, Link can acquire a few dozen bundles of wood, alongside numerous apples.
Side Quests
This material is also required for many Side-Quests in the game, such as Hylian Homeowner and From the Ground Up.