There are several ways that cabinet companies put together their boxes
1. They can be nailed
2. They can be screwed
3. They can be datoed
4. They can be biscuited

You can read some defnitions by clicking going to: http://www.doityourself.com/stry/h2woodjoints

I tried to link it, but couldn't!

Most reputable cabinet companies will do a variety of connections. However, I recommend that you make sure they alway use glued. Nails and Screws will hold together for but will give way after awhile.