D7 Chord
We could talk for hours and hours about the musical theory, the concept, and other technical stuff about the D7 Chord, but for the time being, let's just concentrate on how to play it. Some instructors call this the backwards D because in a sense it kinda is. It's pretty easy to play.
Your first finger must be on the 2nd string on the first fret. Now, your second finger must be on the 3rd string on the second fret, your third finger must be on the 1st string on the second fret as well. The main problem you might encounter at first is that your second finger might mute the second string. Getting your hand used to the position and practicing the chord properly several times will correct that in no time.
Also, remember NOT to hit the sixth and fifth strings, if you do, its perfectly normal to hit the 5th string, it really doesn't damage the chord all that much. It's a common mistake and at times goes by unnoticed, just be careful on not hitting the 6th string, it will cause a messy sound.
This chord is found in many popular songs from all kinds of music it works as a 'progression' part of the song. Learning it will definitely make you a versatile guitar player and give you a wider range of possibilities of what and how to pay.
Once you get a hold of the dominant chords make sure you know them well enough and memorize them, they will prove to be most helpful in the future.
The D7 chord is one of the commonly known as dominant chords. They are called that way because they are found as the 5th chord in a key, classically called as 'Dominant'.