Hi, do we need to play all chords on 2nd fret only? I mean all Am, Dm Em etc or to play on specific fret?
I am a newbi, so little curious.
You need to play those chords the way they are shown because they incorporate open strings. Take the Dm chord as an example - you fret the E, B, and G strings, and play the D (and maybe A) strings open. That's fine because D and A are part of the D minor chord. If you move the chord shape up a fret, it becomes an Eb/D# chord. If you strum that chord the way you do normally it will sound horrible because neither the D or the A notes are part of the Eb chord.
Once you learn barre chords, which won't be for a while if you follow the course, you'll be able to play them at different frets to change the chords/key. For now though, concentrate on learning them and changing to and from them smoothly. If you do want to prepare yourself for later on, practice making all your chords with the middle, ring, and pinky fingers (ie: leave your index finger out). Obviously you can't do that if a chord has four fretted notes, but for the rest of them it will help you out down the line. You don't have to fret them that way all the time, but practicing now and then won't hurt.
Edit: fixed the typo Stitch pointed out *doh*