Q: Why (you might ask)?
A: When you stain wood with tea the wood gets a natural yellow color that is really close to the yelowness that occures when wood ages indoors. So for instance if your repairing a piece of furniture that has become yellow due to age you can use tea to match the color of the old wood on your new pieces and repairs.
The process is simple enough.
You simple make some really strong tea, apply the tea to your new wood and let it dry. Reapply until you reached the desired result!
I originally wrote this surface finishing trick on my blog in finnish