What does it mean to be apprehended under the mental health act?

I was recently apprehended under the mental health act, I don't know why, but I had a knife with me so they assumed I was "crazy". I was brought to the hospital, and the doctor said I was fine, and that nothing was wrong. Was this just a way of scaring me without arresting me, and does this stay on my criminal record? I live in Ontario, and I don't know what this all means. I would really appreciate some answers, that would be great.