It’s called D tuning. The strings are D-G-C-F-A-D. There’s an entire list of different guitar tunings here.

One step down from standard tuning is D tuning .

@SavoirFaire @digitalimpression Is a step down from D Tuning, C Tuning?
Furthermore, can I hold the same shapes as standard tuning onto the lower tunings and with those shapes still produce pleasurable chords?

@dreamwolf Yes: two full steps down from normal tuning, or one full step down from D tuning, would be called C tuning. When using a straightforward alternate tuning like this, your chord shapes will still work. Everything will just be transposed. More elaborate tunings do not come with the same guarantee.

It is a common practice to tune a 12-string in this manner, theoretically to lessen the total tension on the neck and bridge of the guitar; A capo might be used on the second fret to bring the tuning back up to standard.

If you play a “D” chord, for instance, with the strings tuned down a full step, it would sound as a “C” chord. If you tune down much more than that, it might change the tone of the strings.