Question: alternate tuning

Garland,

There are Alternate and open tunings.
Open D tuning = open tuning.
D A D F# A D from fat E, to thin e.
Strum all 6 strings open = D major chord.
Strum all 6 strings 2nd fret = E major chord.
Strum all 6 strings 3rd fret = F major chord.
Strum all 6 strings 5th fret = G major chord.
Etc.

There is simple fingering to change chord from Major to minor or diminished etc.

This tuning is perfect for slide guitar or barr chords.

Keeping it simple, if you want to play blues guitar in open D tuning fingerpicking style, it's best to learn the scales, picking patterns and use tabs.
Their is loads of info on the Web including tabs.

If you are thinking of tuning to open D, learning all the new fingerings for chords to Strum the songs you know, this is not the correct way to use this tuning and far better to stay in standard tuning or tuning down by half a step or full step and keep and play the chord shapes that you already know.

Hope this was a bit of help