What is Zen?

I participated in a special Zen experience which is held during the first week of December.
Why this period of the year? Because, the Buddha opened his enlightenment on December 8th, after 8 days of Zen (sitting meditation) under the linden tree.
 I was a very beginner of this Zen experience, and a Monk taught me ow to practice Zen.
 There are 3 points:
(1) Set up your body (straight in a good sitting position).
(2)Set up your breathing (10 seconds of breathing our and 5 seconds of  breathing in, you will do it 4 times in one minute)
(3)Set up your mind or spirit (that is the most difficult, a Monk said. You look 45 degree below, and try to hear nothing, but if it's difficult, you may close your eyes and imagine a river on which a leaf is going away. You will put all your idle and evil thoughts on that leaf. You will need any power because it goes naturally with the leaf on the river).

After experiencing this Zen for 40 minutes, I felt very healthy both with my body and mind. It is like a purification of both.

Zen is just sit, sit sitting without thinking anything, it is a meditation.
Another Monk said to us, "You can sit like a big tree in a garden." A big tree has many branches and leaves, it has long and tough roots. People come to gather under a big tree.
Experiencing the Zen, you can become like a big tree in a garden!