Android: move character where I touch the screen

I was creating my first unity game for android, and I have a problem.
I want my character to move where I touch the screen,but I have no idea how. I ve read many threads here but they ve confused me even move.
And I also heard that using Transform may cause some errors (like passing through objects etc) that would ruin my game, so is there a way to succeed what I want by adjusting velocity? Thank you in advance!