Timber is a procedural wood material created using Blender’s node system, which means that by changing a few parameters, you can totally change how the material looks. There are two versions, Pro is only compatible with Cycles, whereas Lite is compatible with Eevee and Cycles at the cost of a few features.
To get the most out of Timber Pro:
Expand the .zip file into your material library.
To add the full Timber material to your scene, go File > Append, and then navigate to the Timber.blend file, enter the Material subsection and choose from the material presets you’ll find there. Then click Append from Library.
To add only the individual node groups, go to File > Append, and then navigate to the Timber.blend file, enter the NodeTree subsection and choose the two node groups from there – Timber Config and Timber Surface.
A Brief Overview:
Timber is a fairly advanced procedural material and as such it requires a fair few parameters to control the appearance of the material. For the most part the names of these align with both wood conventions and modelling conventions.
There is more detailed documentation included with each version.