What's Zen?
There's a famous four line description of the zen tradition that has come down to us. This list is attributed to Bodhidharma and it's really supposed to be what sets the Zen tradition apart, what makes Zen different from the rest of Buddhism and what we can keep in mind as zen practitioners.
These four lines express what the zen tradition is and why it's important.
A separate transmission outside the scriptures;
Not dependent on words and letters;
Direct pointing at the human mind;
Seeing one's nature and becoming Buddha.
This sounds serious but maybe it's hard to understand. So I'll go down it line by line.
A separate transmission
This means our practice is in our lives. We aren't simply studying sutras and talking about how great Buddhism is. We are actualizing the teachings in our lives. Hopefully we are also having a dedicated relationship with a teacher and/or a community that can help us on the path.
Not dependent on words and letters
Buddhist writing (and teaching) points in the direction of awakening, but ultimately these things should be viewed as maps and hints, not really as sacred texts. They are to be relied on only in as far as we're trying to use them to point the way. Most writings have come out of someone else's experience, an effort to describe the experience they've had on the path. These are useful and helpful. But the important point is awakening and we won't come to that with intellectual understanding alone.
Direct pointing at the human mind
Our aim in this path is awakening, seeing our true nature. Making efforts to recognize our true nature is the beginning of the path. The fundamental nature of our being is awakening and what we're trying to do is uncover that, not at some later time or in some later life...here and now. Be here now. All the teachings are meant to point us in the direction of our true nature.
Seeing one's nature and becoming Buddha
Seeing one's nature is recognizing your true self. Becoming Buddha is actualizing and embodying that. We don't practice to get somewhere or attain something. We all have Buddha Nature. We have awakening already. We are practicing because that's what Buddhas do. We are all Buddhas. We are dedicated to seeing our awakening and integrating it into our lives.
The Zen approach takes awakening as the path. As practitioners we strive to give ourselves to our training and follow the path that's been laid out for us. Hopefully we can rely on teachers and/or communities and truly throw ourselves into the process of awakening.
That's all there is.